1049: Image gallery rebuild does not complete for some images.

- Only process 'real' files (not folders etc.) for Image gallery.

ImageGallery/src/org/sleuthkit/autopsy/imagegallery/ImageGalleryController.java

@@ -666,7 +666,9 @@ public final class ImageGalleryController {
                         break;
                     }
 
+                    if (f.isFile()) {
                         processFile(f, drawableDbTransaction, caseDbTransaction);
+                    }
  
                     workDone++;
                     progressHandle.progress(f.getName(), workDone);