Bound the original handler to this.

Closes arduino#977

Signed-off-by: Akos Kitta <[email protected]>

Author: Akos Kitta

Diff for: arduino-ide-extension/src/browser/theia/core/application-shell.ts

@@ -130,5 +130,5 @@ DockPanel.prototype.handleEvent = function (event) {
       case 'p-drop':
         return;
   }
-  originalHandleEvent(event);
+  originalHandleEvent.bind(this)(event);
 };