Check for isAttachedToWindow before dispatching touch event

Otherwise we get an IllegalStateException

Fixes: 380318615
Test: repos in production
Flag: EXEMPT bugfix
Change-Id: Id72b76ab288f40ee50ba8485d4b0636c525e22e3
diff --git a/quickstep/src/com/android/launcher3/taskbar/navbutton/NearestTouchFrame.java b/quickstep/src/com/android/launcher3/taskbar/navbutton/NearestTouchFrame.java
index bbf08bf..844f1af 100644
--- a/quickstep/src/com/android/launcher3/taskbar/navbutton/NearestTouchFrame.java
+++ b/quickstep/src/com/android/launcher3/taskbar/navbutton/NearestTouchFrame.java
@@ -194,6 +194,7 @@
                 event.offsetLocation(mTouchingChild.getWidth() / 2 - x,
                         mTouchingChild.getHeight() / 2 - y);
                 return mTouchingChild.getVisibility() == VISIBLE
+                        && mTouchingChild.isAttachedToWindow()
                         && mTouchingChild.dispatchTouchEvent(event);
             }
         }