title: SharedPreferences error in Flutter
body: <p>I was using <code>shared_preferences</code> plugin in my Flutter application. From one moment (probably after Flutter upgrade), it started to throw an exception:</p>
  
  <pre><code>E/flutter (27778): [ERROR:topaz/lib/tonic/logging/dart_error.cc(16)] Unhandled exception:
  E/flutter (27778): type '_InternalLinkedHashMap' is not a subtype of type 'Map&lt;String, Object&gt;' where
  E/flutter (27778):   _InternalLinkedHashMap is from dart:collection
  E/flutter (27778):   Map is from dart:core
  E/flutter (27778):   String is from dart:core
  E/flutter (27778):   Object is from dart:core
  E/flutter (27778): 
  E/flutter (27778): #0      SharedPreferences.getInstance (package:shared_preferences/shared_preferences.dart)
  E/flutter (27778): &lt;asynchronous suspension&gt;
  E/flutter (27778): #1      loadFirstUse (**path**/lib/main.dart:29:53)
  E/flutter (27778): &lt;asynchronous suspension&gt;
  E/flutter (27778): #2      main (**path**/lib/main.dart:17:9)
  E/flutter (27778): &lt;asynchronous suspension&gt;
  E/flutter (27778): #3      _startIsolate.&lt;anonymous closure&gt; (dart:isolate/runtime/libisolate_patch.dart:279:19)
  E/flutter (27778): #4      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)
  </code></pre>
  
  <p>It happens when I simple try to create instance of SharedPreferences: </p>
  
  <pre><code>SharedPreferences prefs = await SharedPreferences.getInstance();
  </code></pre>
  
  <p>I was trying to find root of the problem, but was unable to find it. Thank you for any help.</p>
  
  <p>EDIT: I am using   <code>shared_preferences: "^0.4.0"</code></p>