Fix NPE in ForwardingListener

Caused by a postDelayed() and lack of
null check

BUG: 29992695
Change-Id: I0c7454c6098dd1ead1545cc4603da6ff5261b666
diff --git a/v7/appcompat/src/android/support/v7/widget/ForwardingListener.java b/v7/appcompat/src/android/support/v7/widget/ForwardingListener.java
index 1ad9218..6d9885c 100644
--- a/v7/appcompat/src/android/support/v7/widget/ForwardingListener.java
+++ b/v7/appcompat/src/android/support/v7/widget/ForwardingListener.java
@@ -103,6 +103,10 @@
         return forwarding || wasForwarding;
     }
 
+    public void onDetachedFromWindow() {
+        clearCallbacks();
+    }
+
     /**
      * Called when forwarding would like to start.
      * <p>
@@ -293,7 +297,9 @@
         @Override
         public void run() {
             final ViewParent parent = mSrc.getParent();
-            parent.requestDisallowInterceptTouchEvent(true);
+            if (parent != null) {
+                parent.requestDisallowInterceptTouchEvent(true);
+            }
         }
     }