Vcs: Fix compile for Qt < 5.4

Introduced with 7a05c9ea5b

Change-Id: Iddf3c3ace15e1f79acc59d4024f796428b1a4713
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/vcsbase/vcsbaseeditor.cpp

@@ -980,7 +980,7 @@ void VcsBaseEditorWidget::contextMenuEvent(QContextMenuEvent *e)
     default:
         break;
     }
-    connect(this, &QObject::destroyed, menu, &QObject::deleteLater);
+    connect(this, &QObject::destroyed, menu.data(), &QObject::deleteLater);
     menu->exec(e->globalPos());
     delete menu;
 }