Fix bugs in "indexOfVideoWithSource"

[feklee]

Proposal (return statements originally wrong, and no check if index list is empty):

 // If existent, returns the index of a video clip that shows a transition
 // from the specified configuration. Otherwise returns false.
 function indexOfVideoWithSource(configurationIndex) {
     var sourceConfigurationIndex, indexOfVideo = false;

     $.each(videoIndexesList, function (key, videoIndexes) {
         sourceConfigurationIndex = parseInt(key, 10);
         if (sourceConfigurationIndex === configurationIndex &&
             videoIndexesList[key].length > 0) {
             videoIndexes = videoIndexesList[key]; // non-empty
             indexOfVideo = anyOwnPropertyValue(videoIndexes); // any is OK
             return indexOfVideo;
         }
     });

     return false; // nothing found
 }

Note: This issue may not be relevant anymore - check!