title: Flutter exception 'package:flutter/src/widgets/sliver.dart': Failed assertion 'child != null' is not true
body: <p>I'm getting this Exception from flutter package sliver.dart, when I navigate to a new page. </p>
  
  <p>All of this was working fine, but later I tried to add multiple features to it like connecting sqlite database, I thought that would be the problem So I tried to go back to the last working state of my app by removing every additional code. But unfortunately it's still giving me this error. Even if you look at my frontend code below there is nothing special right now it's just displaying data that I already have in an object.</p>
  
  <p>Tried completely reinstalling the app but no solution still.</p>
  
  <pre><code>Running "flutter packages get" in heron...                          1.5s
  Launching lib\main.dart on Android SDK built for x86 in debug mode...
  Built build\app\outputs\apk\debug\app-debug.apk.
  D/        (23206): HostConnection::get() New Host Connection established 0xa4b249c0, tid 23228
  D/EGL_emulation(23206): eglMakeCurrent: 0xa6594cc0: ver 3 0 (tinfo 0x94a360d0)
  I/flutter (23206): TV GET Requested
  I/flutter (23206): Movie GET Requested
  I/flutter (23206): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
  I/flutter (23206): The following assertion was thrown during performLayout():
  I/flutter (23206): 'package:flutter/src/widgets/sliver.dart': Failed assertion: line 553 pos 12: 'child != null': is
  I/flutter (23206): not true.
  I/flutter (23206): 
  I/flutter (23206): Either the assertion indicates an error in the framework itself, or we should provide substantially
  I/flutter (23206): more information in this error message to help you determine and fix the underlying cause.
  I/flutter (23206): In either case, please report this assertion by filing a bug on GitHub:
  I/flutter (23206):   https://github.com/flutter/flutter/issues/new?template=BUG.md
  I/flutter (23206): 
  I/flutter (23206): When the exception was thrown, this was the stack:
  I/flutter (23206): #2      SliverChildListDelegate.build 
  I/flutter (23206): #3      SliverMultiBoxAdaptorElement._build.&lt;anonymous closure&gt; 
  I/flutter (23206): #4      _HashMap.putIfAbsent (dart:collection/runtime/libcollection_patch.dart:137:29)
  I/flutter (23206): #5      SliverMultiBoxAdaptorElement._build 
  I/flutter (23206): #6      SliverMultiBoxAdaptorElement.createChild.&lt;anonymous closure&gt; 
  I/flutter (23206): #7      BuildOwner.buildScope 
  I/flutter (23206): #8      SliverMultiBoxAdaptorElement.createChild 
  I/flutter (23206): #9      RenderSliverMultiBoxAdaptor._createOrObtainChild.&lt;anonymous closure&gt; 
  I/flutter (23206): #10     RenderObject.invokeLayoutCallback.&lt;anonymous closure&gt; 
  I/flutter (23206): #11     PipelineOwner._enableMutationsToDirtySubtrees 
  I/flutter (23206): #12     RenderObject.invokeLayoutCallback 
  I/flutter (23206): #13     RenderSliverMultiBoxAdaptor._createOrObtainChild 
  I/flutter (23206): #14     RenderSliverMultiBoxAdaptor.insertAndLayoutChild 
  I/flutter (23206): #15     RenderSliverList.performLayout.advance 
  I/flutter (23206): #16     RenderSliverList.performLayout 
  I/flutter (23206): #17     RenderObject.layout 
  I/flutter (23206): #18     RenderSliverPadding.performLayout 
  I/flutter (23206): #19     RenderObject.layout 
  I/flutter (23206): #20     RenderViewportBase.layoutChildSequence 
  I/flutter (23206): #21     RenderViewport._attemptLayout 
  I/flutter (23206): #22     RenderViewport.performLayout 
  I/flutter (23206): #23     RenderObject.layout 
  I/flutter (23206): #24     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #25     RenderObject.layout 
  I/flutter (23206): #26     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #27     RenderObject.layout 
  I/flutter (23206): #28     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #29     RenderObject.layout 
  I/flutter (23206): #30     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #31     RenderObject.layout 
  I/flutter (23206): #32     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #33     RenderObject.layout 
  I/flutter (23206): #34     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #35     RenderObject.layout 
  I/flutter (23206): #36     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #37     RenderObject.layout 
  I/flutter (23206): #38     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #39     RenderObject.layout 
  I/flutter (23206): #40     RenderPadding.performLayout 
  I/flutter (23206): #41     RenderObject.layout 
  I/flutter (23206): #42     MultiChildLayoutDelegate.layoutChild 
  I/flutter (23206): #43     _ScaffoldLayout.performLayout 
  I/flutter (23206): #44     MultiChildLayoutDelegate._callPerformLayout 
  I/flutter (23206): #45     RenderCustomMultiChildLayoutBox.performLayout 
  I/flutter (23206): #46     RenderObject.layout 
  I/flutter (23206): #47     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #48     RenderObject.layout 
  I/flutter (23206): #49     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #50     _RenderCustomClip.performLayout 
  I/flutter (23206): #51     RenderObject.layout 
  I/flutter (23206): #52     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #53     RenderObject.layout 
  I/flutter (23206): #54     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #55     RenderObject.layout 
  I/flutter (23206): #56     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #57     RenderObject.layout 
  I/flutter (23206): #58     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #59     RenderObject.layout 
  I/flutter (23206): #60     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #61     RenderObject.layout 
  I/flutter (23206): #62     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #63     RenderObject.layout 
  I/flutter (23206): #64     _RenderProxyBox&amp;RenderBox&amp;RenderObjectWithChildMixin&amp;RenderProxyBoxMixin.performLayout 
  I/flutter (23206): #65     RenderObject.layout 
  I/flutter (23206): #66     RenderOffstage.performLayout 
  I/flutter (23206): #67     RenderObject.layout 
  I/flutter (23206): #68     RenderStack.performLayout 
  I/flutter (23206): #69     RenderObject._layoutWithoutResize 
  I/flutter (23206): #70     PipelineOwner.flushLayout 
  I/flutter (23206): #71     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding&amp;PaintingBinding&amp;SemanticsBinding&amp;RendererBinding.drawFrame 
  I/flutter (23206): #72     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding&amp;PaintingBinding&amp;SemanticsBinding&amp;RendererBinding&amp;WidgetsBinding.drawFrame 
  I/flutter (23206): #73     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding&amp;PaintingBinding&amp;SemanticsBinding&amp;RendererBinding._handlePersistentFrameCallback 
  I/flutter (23206): #74     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding._invokeFrameCallback 
  I/flutter (23206): #75     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding.handleDrawFrame 
  I/flutter (23206): #76     _WidgetsFlutterBinding&amp;BindingBase&amp;GestureBinding&amp;ServicesBinding&amp;SchedulerBinding._handleDrawFrame 
  I/flutter (23206): #80     _invoke (dart:ui/hooks.dart:209:10)
  I/flutter (23206): #81     _drawFrame (dart:ui/hooks.dart:168:3)
  I/flutter (23206): (elided 5 frames from class _AssertionError and package dart:async)
  I/flutter (23206): 
  I/flutter (23206): The following RenderObject was being processed when the exception was fired:
  I/flutter (23206):   RenderSliverList#19980 relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT
  I/flutter (23206):   creator: SliverList ← MediaQuery ← SliverPadding ← Viewport ← IgnorePointer-[GlobalKey#7290e] ←
  I/flutter (23206):   Semantics ← Listener ← _GestureSemantics ←
  I/flutter (23206):   RawGestureDetector-[LabeledGlobalKey&lt;RawGestureDetectorState&gt;#9ea0f] ← _ScrollableScope ←
  I/flutter (23206):   _ScrollSemantics-[GlobalKey#aa43f] ← RepaintBoundary ← ⋯
  I/flutter (23206):   parentData: paintOffset=Offset(0.0, 0.0) (can use size)
  I/flutter (23206):   constraints: SliverConstraints(AxisDirection.down, GrowthDirection.forward, ScrollDirection.idle,
  I/flutter (23206):   scrollOffset: 0.0, remainingPaintExtent: 598.4, crossAxisExtent: 381.4, crossAxisDirection:
  I/flutter (23206):   AxisDirection.right, viewportMainAxisExtent: 598.4, remainingCacheExtent: 848.4 cacheOrigin: 0.0 )
  I/flutter (23206):   geometry: null
  I/flutter (23206):   currently live children: 0 to 2
  I/flutter (23206): This RenderObject had the following descendants (showing up to depth 5):
  I/flutter (23206):   RenderIndexedSemantics#6d89b relayoutBoundary=up3 NEEDS-PAINT
  I/flutter (23206):     RenderRepaintBoundary#41a15 relayoutBoundary=up4 NEEDS-PAINT
  I/flutter (23206):       RenderConstrainedBox#f6331 relayoutBoundary=up5 NEEDS-PAINT
  I/flutter (23206):         RenderStack#1d492 NEEDS-PAINT
  I/flutter (23206):           RenderSemanticsAnnotations#dee5b relayoutBoundary=up1 NEEDS-PAINT
  I/flutter (23206):           RenderSemanticsAnnotations#75402 NEEDS-PAINT
  I/flutter (23206):           RenderConstrainedBox#553a7 relayoutBoundary=up1 NEEDS-PAINT
  I/flutter (23206):   RenderIndexedSemantics#dbd86 relayoutBoundary=up3 NEEDS-PAINT
  I/flutter (23206):     RenderRepaintBoundary#d9292 relayoutBoundary=up4 NEEDS-PAINT
  I/flutter (23206):       RenderDecoratedBox#fdc4c relayoutBoundary=up5 NEEDS-PAINT
  I/flutter (23206):         RenderSemanticsGestureHandler#fac22 relayoutBoundary=up6 NEEDS-PAINT
  I/flutter (23206):           RenderPointerListener#bca58 relayoutBoundary=up7 NEEDS-PAINT
  I/flutter (23206):   RenderIndexedSemantics#dc7c8 relayoutBoundary=up3 NEEDS-PAINT
  I/flutter (23206):     RenderRepaintBoundary#f0361 relayoutBoundary=up4 NEEDS-PAINT
  I/flutter (23206):       RenderSemanticsGestureHandler#29897 relayoutBoundary=up5 NEEDS-PAINT
  I/flutter (23206):         RenderPointerListener#e3417 relayoutBoundary=up6 NEEDS-PAINT
  I/flutter (23206):           RenderSemanticsAnnotations#69a6f relayoutBoundary=up7 NEEDS-PAINT
  I/flutter (23206): ════════════════════════════════════════════════════════════════════════════════════════════════════
  I/flutter (23206): Another exception was thrown: NoSuchMethodError: The getter 'scrollOffsetCorrection' was called on null.
  I/flutter (23206): Another exception was thrown: NoSuchMethodError: The method 'debugAssertIsValid' was called on null.
  I/flutter (23206): Another exception was thrown: NoSuchMethodError: The getter 'visible' was called on null.
  
  </code></pre>
  
  <p>I have divided my code into two pages</p>
  
  <p>front end - <a href="https://gist.github.com/purplecandy/54234b2080f27b43075ef289489ecf5b" rel="nofollow noreferrer">https://gist.github.com/purplecandy/54234b2080f27b43075ef289489ecf5b</a></p>
  
  <p>functions - <a href="https://gist.github.com/purplecandy/8d7a8cb0e3e001d6517ddc21dde72256" rel="nofollow noreferrer">https://gist.github.com/purplecandy/8d7a8cb0e3e001d6517ddc21dde72256</a></p>
  
  <p>pubspec - <a href="https://gist.github.com/purplecandy/06be5d9a521239052a25cbe6e042471b" rel="nofollow noreferrer">https://gist.github.com/purplecandy/06be5d9a521239052a25cbe6e042471b</a></p>
  
  <p>Can anyone give me some insight what is causing this issue? Where am I wrong? Or just explain the error to me</p>