title: Assertion failed in PDFTron iOS
body: <p>I have integrated the PDFTron library in my iOS Application and followed the instruction mentioned in documentation(<strong><a href="https://blog.pdftron.com/2013/07/19/getting-started-on-ios/" rel="nofollow">https://blog.pdftron.com/2013/07/19/getting-started-on-ios/</a></strong>), application is working fine when I am using the local pdf files but application is crashing each time in below scenario</p>
  
  <p>1) Downloaded pdf files from url, stored in document directory and display using the PDFTron.</p>
  
  <p>I have got following the error log:</p>
  
  <blockquote>
    <p>function -[PTPDFViewCtrl RemoveAllThumbnails], file
    /Users/PDFTron/PDFNet_6.5/PDFTron/iOS/Control/PDFViewCtrl.m, line
    1744. (lldb) bt 
    * thread #23: tid = 0x12491, 0x000000010aa43002 libsystem_kernel.dylib<code>__pthread_kill + 10, stop reason = signal
    SIGABRT
        frame #0: 0x000000010aa43002 libsystem_kernel.dylib</code>__pthread_kill + 10
        frame #1: 0x000000010aa095c5 libsystem_pthread.dylib<code>pthread_kill + 90
        frame #2: 0x000000010a799cec libsystem_c.dylib</code>abort + 129
        frame #3: 0x000000010a761bdc libsystem_c.dylib<code>__assert_rtn + 321
        frame #4: 0x00000001041177c4 BW - Internal</code>-[PTPDFViewCtrl RemoveAllThumbnails] + 94
        frame #5: 0x0000000104113daf BW - Internal`-[PTPDFViewCtrl SetDoc:] + 178</p>
  </blockquote>
  
  <p>I have tried lock and unlocking the document but still I am getting same error and any help is appreciated.</p>