Probably fix intermittent irreproducible NPE

We're seeing this NPE in all OS versions from 2.3 to 4.3 (the vast majority in 2.3.6), ultimately ending up in View.dispatchRestoreInstanceState. 'container' seems to be the only object invoked with a method in the versions of dispatchRestoreInstanceState() I've examined.

Caused by: java.lang.NullPointerException
1	 android.view.View.dispatchRestoreInstanceState	 View.java, line 6473
2	 android.view.ViewGroup.dispatchRestoreInstanceState	 ViewGroup.java, line 1211
3	 android.view.View.restoreHierarchyState	 View.java, line 6457
4	 com.actionbarsherlock.internal.view.menu.MenuBuilder.restoreActionViewStates	 SourceFile, line 361
5	 com.actionbarsherlock.internal.ActionBarSherlockCompat.preparePanel	 SourceFile, line 503
6	 com.actionbarsherlock.internal.ActionBarSherlockCompat.dispatchInvalidateOptionsMenu	 SourceFile, line 272
7	 com.actionbarsherlock.app.SherlockFragmentActivity.invalidateOptionsMenu	 SourceFile, line 150
8	 com.actionbarsherlock.app.SherlockFragmentActivity.supportInvalidateOptionsMenu	 SourceFile, line 156