Merge pull request #487 from IanDelMar/patch-3

Check whether $args['items_wrap'] is set

Author: pattonwebz

class-wp-bootstrap-navwalker.php

@@ -391,11 +391,12 @@ public static function fallback( $args ) {
  * @return array $args The altered nav instance arguments.
  */
 public function add_schema_to_navbar_ul( $args ) {
-$wrap = $args['items_wrap'];
-if ( strpos( $wrap, 'SiteNavigationElement' ) === false ) {
-$args['items_wrap'] = preg_replace( '/(>).*>?\%3\$s/', ' itemscope itemtype="http://www.schema.org/SiteNavigationElement"$0', $wrap );
+if ( isset( $args['items_wrap'] ) ) {
+$wrap = $args['items_wrap'];
+if ( strpos( $wrap, 'SiteNavigationElement' ) === false ) {
+$args['items_wrap'] = preg_replace( '/(>).*>?\%3\$s/', ' itemscope itemtype="http://www.schema.org/SiteNavigationElement"$0', $wrap );
+}
 }
-
 return $args;
 }