Listview filter: Check if var listview is defined. Fixes jquery-archive#5696 and jquery-archive#5643

The listviewcreate event bubbles up which causes an error if a listview is nested in an UL or OL without data-role="listview".

Author: jaspermdegroot

js/widgets/listview.filter.js

@@ -20,11 +20,10 @@ var defaultFilterCallback = function( text, searchValue, item ) {
 $.mobile.listview.prototype.options.filterCallback = defaultFilterCallback;
 
 $.mobile.document.delegate( "ul, ol", "listviewcreate", function() {
-
 	var list = $( this ),
 		listview = list.data( "mobile-listview" );
 
-	if ( !listview.options.filter ) {
+	if ( !listview || !listview.options.filter ) {
 		return;
 	}