title: Navigation Back Button Crash
body: <p>My application basically gets user input, adds it to tableview and goes to second view controller which has scrollview. User input is simply city name, and the app delivers detailed weather information in the scrollview. </p>
  
  <p>App crashes when user scrolls then click native back button. Does any of you have any idea why this happens? By the way, if I do not scroll, then click back button does not crash.</p>
  
  <p>My Project solution could be downloaded in the following link <a href="https://docs.google.com/file/d/0B2Yf2EqUAx61RGUtcGREMXJSYzQ/edit" rel="nofollow noreferrer">Download Solution</a></p>
  
  <p>Here is the crash screenshot
  <img src="https://i.stack.imgur.com/FGQmT.png" alt="enter image description here"></p>
  
  <p><img src="https://i.stack.imgur.com/RUKKw.png" alt="enter image description here"></p>
  
  <p><strong>Backtrace -</strong></p>
  
  <pre><code>(lldb) bt
  * thread #1: tid = 0x6cac58, 0x000000010e1eb00b libobjc.A.dylib`objc_msgSend + 11, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=EXC_I386_GPFLT)
      frame #0: 0x000000010e1eb00b libobjc.A.dylib`objc_msgSend + 11
      frame #1: 0x000000010cb25c9c UIKit`-[UIScrollView(UIScrollViewInternal) _notifyDidScroll] + 56
      frame #2: 0x000000010cb16262 UIKit`-[UIScrollView setContentOffset:] + 645
      frame #3: 0x000000010cb2ab9c UIKit`-[UIScrollView(UIScrollViewInternal) _adjustContentOffsetIfNecessary] + 1445
      frame #4: 0x000000010cb27d2b UIKit`-[UIScrollView(UIScrollViewInternal) _stopScrollingNotify:pin:tramplingDragFlags:] + 417
      frame #5: 0x000000010cb16af6 UIKit`-[UIScrollView removeFromSuperview] + 32
      frame #6: 0x000000010caf0d19 UIKit`-[UIView dealloc] + 404
      frame #7: 0x000000010e1e98cd libobjc.A.dylib`(anonymous namespace)::AutoreleasePoolPage::pop(void*) + 591
      frame #8: 0x000000010e432346 CoreFoundation`_CFAutoreleasePoolPop + 22
      frame #9: 0x000000010e466473 CoreFoundation`__CFRunLoopRun + 2051
      frame #10: 0x000000010e465a06 CoreFoundation`CFRunLoopRunSpecific + 470
      frame #11: 0x0000000110c539f0 GraphicsServices`GSEventRunModal + 161
      frame #12: 0x000000010ca92550 UIKit`UIApplicationMain + 1282
    * frame #13: 0x000000010c75c623 weather_app`main(argc=1, argv=0x00007fff534da2e0) + 115 at main.m:16
      frame #14: 0x000000010ecbf145 libdyld.dylib`start + 1
  (lldb) 
  </code></pre>