Merge branch 'commit-image-branch' into 'master'

Fixed JS issue with diff image loading

Fixes #1323

Whilst I couldn't reproduce the error locally, I did manage to get the same JS error message that was in the live env.

See merge request !463

app/assets/javascripts/commit/image-file.js.coffee

@@ -119,6 +119,7 @@ class @ImageFile
 
   requestImageInfo: (img, callback) ->
     domImg = img.get(0)
+    if domImg
       if domImg.complete
         callback.call(this, domImg.naturalWidth, domImg.naturalHeight)
       else