title: Terminating app due to uncaught exception 'CALayerInvalidGeometry', reason: 'CALayer bounds contains NaN: [0 nan; 280 524]'
body: <p>I am developing a book app where users can change the font size on the TextView.</p>
  
  <p>when users change the font size, the app save the current text position not to change that after users did changing font size.</p>
  
  <p>It works fine in most cases, but sometimes, when users change the font size, the app gets this kind of error, and I still can't tell how to fix this.</p>
  
  <blockquote>
    <p>Terminating app due to uncaught exception 'CALayerInvalidGeometry', reason: 'CALayer bounds contains NaN: [0 nan; 280 524]'
    <em>*</em> First throw call stack:
    (0x3231e3e7 0x3a019963 0x3231e307 0x33edb4d7 0x33edb30d 0x3419141f 0x3419b82f 0x342d1cf1 0x3414f80d 0xe7bf1 0xe607d 0xfad35 0x34218087 0x34218111 0x34218087 0x3421803b 0x34218015 0x342178cb 0x34217db9 0x341405f9 0x3412d8e1 0x3412d1ef 0x35e455f7 0x35e45227 0x322f33e7 0x322f338b 0x322f220f 0x3226523d 0x322650c9 0x35e4433b 0x341812b9 0xdf9f1 0xdf978)
    libc++abi.dylib: terminate called throwing an exception</p>
  </blockquote>
  
  <p>I also can't reproduce this issue 100% since this issue happens occasionally.</p>
  
  <p>This is the code.  Does anybody have an idea to fix this?  Thanks in advance.</p>
  
  <pre><code>- (UITextRange *)getCurrentTextRange:(UITextView *)textView {
  
      CGRect bounds               = textView.bounds;
      UITextPosition *start       = [textView characterRangeAtPoint:bounds.origin].start;
      UITextPosition *end         = [textView positionFromPosition:start offset:1];
      UITextRange *textRange      = [textView textRangeFromPosition:start toPosition:end];
  
      return textRange;
  }
  
  - (void)changeFontSize:(UIButton*)button {
  
      UITextRange *textRange  = [self getCurrentTextRange:_textView];
      int fontSize            = [[NSUserDefaults standardUserDefaults] integerForKey:@"fontSize"];
  
      //button.tag == 1 =&gt; decreaseFontSize
      if (button.tag == 1) {
  
          //set a minimum size
          if (fontSize &lt;= [LSUniversalManager getFontSizeForMinimum]) {
              return;
          }
  
          fontSize--;
  
      //button.tag == 2 =&gt; increaseFontSize
      } else if (button.tag == 2) {        
          fontSize++;
      }
  
      _textView.font      = [UIFont systemFontOfSize:fontSize];
      [[NSUserDefaults standardUserDefaults] setInteger:fontSize forKey:@"fontSize"];
  
      //avoid shifting the scroll position after changing font size
      CGRect rect = [_textView firstRectForRange:textRange];
      [_textView setContentOffset:CGPointMake(0, rect.origin.y)];
  }
  </code></pre>