Ticket #28155: 28155.5.diff

src/wp-includes/wp-db.php

@@ -1325 +1325 @@
                 if ( $this->use_mysqli && $this->result instanceof mysqli_result ) {
                         mysqli_free_result( $this->result );
                         $this->result = null;
-
+                        // Sanity check before using the handle
+                        if ( empty( $this->dbh ) || !( $this->dbh instanceof mysqli ) ) {
+                                return;
+                        }
                         // Clear out any results from a multi-query
                         while ( mysqli_more_results( $this->dbh ) ) {
                                 mysqli_next_result( $this->dbh );