Fix bug with selection clearing triggered when dev tools open

Change-Id: I62d20ee830af8f88ce816736d71ab78da90fed9d

appinventor/appengine/src/com/google/appinventor/client/widgets/dnd/DragSourceSupport.java

@@ -166,7 +166,7 @@ public final class DragSourceSupport implements MouseListener {
             sel.removeAllRanges();
           }
           if (sel.collapse) {
-            sel.collapse();
+            sel.collapse(null, 0);
           }
         }
       }