Add missing null check

Change-Id: I05e288762c00d80f4c0842584daa88c205196b6f

Author: jreck

core/java/android/webkit/WebViewClassic.java

@@ -4362,7 +4362,9 @@ public void onDraw(Canvas canvas) {
     }
 
     private void removeTouchHighlight() {
-        mWebViewCore.removeMessages(EventHub.HIT_TEST);
+        if (mWebViewCore != null) {
+            mWebViewCore.removeMessages(EventHub.HIT_TEST);
+        }
         mPrivateHandler.removeMessages(HIT_TEST_RESULT);
         setTouchHighlightRects(null);
     }