Fix issue with adding widget with config activity to empty screen (issue 11381059)

Change-Id: Ic7eecb30422e7a6cf35ebe8470d9eba8752d406e
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index f721571..3290d8e 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -754,10 +754,14 @@
                 };
             } else {
                 result = resultCode;
+                final CellLayout dropLayout =
+                        (CellLayout) mWorkspace.getScreenWithId(mPendingAddInfo.screenId);
+                dropLayout.setDropPending(true);
                 onComplete = new Runnable() {
                     @Override
                     public void run() {
                         completeTwoStageWidgetDrop(result, appWidgetId);
+                        dropLayout.setDropPending(false);
                     }
                 };
             }