MultitaskingView: Stop events from propagating while closed

This fixes an issue where you could initiate a drag and drop while
the workspace switch animation finished which looks very strange.

Author: leolost2605

src/Widgets/MultitaskingView/MultitaskingView.vala

@@ -508,5 +508,18 @@ namespace Gala {
 
             return true;
         }
+
+        public override bool captured_event (Clutter.Event event) {
+            /* If we aren't open but receive events this means we are animating closed
+             * or we are finishing a workspace switch animation. In any case we want to
+             * prevent a drag and drop to start for the window clones which can happen
+             * pretty easily if you click on one while the animation finishes.
+             */
+            if (!opened) {
+                return Clutter.EVENT_STOP;
+            }
+
+            return Clutter.EVENT_PROPAGATE;
+        }
     }
 }