filter_api: ensure that the free_text where clauses are always ANDed

Fixes #15573: One query can be issued via current Mantis interface to
take down site

core/filter_api.php

@@ -1996,8 +1996,7 @@ function filter_get_bug_rows( &$p_page_number, &$p_per_page, &$p_page_count, &$p
 		# add text query elements to arrays
 		if ( !$t_first ) {
 			$t_from_clauses[] = "$t_bug_text_table";
-			$t_where_clauses[] = "$t_bug_table.bug_text_id = $t_bug_text_table.id";
-			$t_where_clauses[] = $t_textsearch_where_clause;
+			$t_where_clauses[] = "$t_bug_table.bug_text_id = $t_bug_text_table.id AND $t_textsearch_where_clause";
 			$t_join_clauses[] = " LEFT JOIN $t_bugnote_table ON $t_bug_table.id = $t_bugnote_table.bug_id";
 			$t_join_clauses[] = " LEFT JOIN $t_bugnote_text_table ON $t_bugnote_table.bugnote_text_id = $t_bugnote_text_table.id";
 		}