AddFooter(View, Object, boolean) is updated to add the view to the inter...

Had a test case like,

StickyListHeaderListView listView;
listView.addFooterView(footerView, myFooterData, true);

....
if (listView.containsFooterView(footerView)) {
   listView.removeFooterView(footerView);
}

// or worse
listView.removeFooterView(footerView); // Crashes since WrapperList.mFooterViews is null.

WrapperList.removeFooter assumes the mFooterViews list is non null, except that addFooterView(View, Object, boolean) was not overridden to update mFooterViews list. This just makes the implementation more consistent.