[ticket/11469] Return after sql_multi_insert when multi_insert is false

PHPBB3-11469

phpBB/includes/db/sql_insert_buffer.php

@@ -69,6 +69,7 @@ class phpbb_db_sql_insert_buffer
 			// Pass data on to sql_multi_insert right away which will
 			// immediately send an INSERT INTO query to the database.
 			$this->db->sql_multi_insert($this->table_name, array($row));
+			return;
 		}
 
 		$this->buffer[] = $row;