Ticket #15350: dont-assume-tax-operator.15350.diff

wp-includes/query.php

@@ -1572 +1572 @@
                 $q['tax_query'] = $tax_query;
 
                 foreach ( $q['tax_query'] as $query ) {
-                        if ( 'IN' == $query['operator'] ) {
+                        if ( isset( $query['operator'] ) && 'IN' == $query['operator'] ) {
                                 switch ( $query['taxonomy'] ) {
                                         case 'category':
                                                 $this->is_category = true;