Protect against focus changes after .destroy()

 Bug: 7026042

Change-Id: I656b612a4b5304225863d3100a98bf2b97d9890d

Author: jreck

core/java/android/webkit/WebViewClassic.java

@@ -6981,6 +6981,8 @@ private void overrideLoading(String url) {
 
     @Override
     public boolean requestFocus(int direction, Rect previouslyFocusedRect) {
+        // Check if we are destroyed
+        if (mWebViewCore == null) return false;
         // FIXME: If a subwindow is showing find, and the user touches the
         // background window, it can steal focus.
         if (mFindIsUp) return false;