Bug 1096958 - Part 2: Null mGrid's OnItemClickListener when destroying the view. r=liuche

This prevents the listener from being called after some necessary resources are
destroyed.

There is probably a better solution such as removing the listeners after a
successful run, but I'm unsure of the side effects. We know this solution works
because of precedent (bug 930160) so let's go with the quick & easy for now.

--HG--
extra : rebase_source : 9086ddc50a321f63503dd131dd2c78e73732d200

mobile/android/base/home/TopSitesPanel.java

@@ -304,11 +304,12 @@ public class TopSitesPanel extends HomeFragment {
     public void onDestroyView() {
         super.onDestroyView();
 
-        // Discard any additional item clicks on the list
-        // as the panel is getting destroyed (see bug 930160).
+        // Discard any additional item clicks on the list as the
+        // panel is getting destroyed (see bugs 930160 & 1096958).
         mList.setOnItemClickListener(null);
-        mList = null;
+        mGrid.setOnItemClickListener(null);
 
+        mList = null;
         mGrid = null;
         mListAdapter = null;
         mGridAdapter = null;