title: Not a PNG filCommand copypng emitted errors but did not return a nonzero exit code to indicate failure
body: <p>I am getting following error while adding images the running the project on iPad.
  It worked fine on simulator with all images but on iPad its running but showing no images.</p>
  
  <pre><code>CopyPNGFile /Users/user/Library/Developer/Xcode/DerivedData/RImageGallery-cmwaittvclhwgxfpcoarddipyliv/Build/Products/Debug-iphoneos/RImageGallery.app/Default.png PhotoBrowserDemo/Default.png
      cd /Users/user/Desktop/Demo
      setenv PATH "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
      /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/copypng -compress "" /Users/user/Desktop/Demo/PhotoBrowserDemo/Default.png /Users/user/Library/Developer/Xcode/DerivedData/RImageGallery-cmwaittvclhwgxfpcoarddipyliv/Build/Products/Debug-iphoneos/RImageGallery.app/Default.png
  
     Not a PNG filCommand /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/copypng emitted errors but did not return a nonzero exit code to indicate failure
  
  
  
  
  (null): While reading /Users/user/Desktop/Demo/PhotoBrowserDemo/Default.png pngcrush caught libpng error:
  
  
  
  
  (null): Could not find file: /Users/user/Library/Developer/Xcode/DerivedData/RImageGallery-cmwaittvclhwgxfpcoarddipyliv/Build/Products/Debug-iphoneos/RImageGallery.app/Default.png
  
  
  
  
  Command /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/copypng emitted errors but did not return a nonzero exit code to indicate failure
  </code></pre>