Fix FineUploader to handle cancellations in the onError() callback

Calling cancel() in the onError() callback would cause an error as the
upload handler tries to clear the upload’s xhr requests after cancel
already clears them.

js/components/ascribe_uploader/vendor/s3.fine-uploader.js

@@ -4399,7 +4399,9 @@ qq.UploadHandlerController = function(o, namespace) {
                     }
                 )
                     .done(function() {
+                        if (handler._getFileState(id)) {
                             handler.clearXhr(id, chunkIdx);
+                        }
                     }) ;
             }
         }