PiP: Early return on MenusAlgorithm if there are no views.

If there are any missing views, there's nothing to do.

Bug: 161760276
Test: None
Change-Id: If63a1e855b1924dab981dd55b7bc663ed9ee26e5

libs/WindowManager/Shell/src/com/android/wm/shell/pip/phone/PipMenuIconsAlgorithm.java

@@ -60,6 +60,7 @@ public class PipMenuIconsAlgorithm {
         if (mViewRoot == null || mTopEndContainer == null || mDragHandle == null
                 || mSettingsButton == null || mDismissButton == null) {
             Log.e(TAG, "One if the required views is null.");
+            return;
         }
 
         //We only need to calculate the layout once since it does not change.