Follow-up fix to MDEV-16865: InnoDB fts_query() ignores KILL

fts_query(): Remove a redundant condition (result will never be NULL),
and instead check if *result is NULL, to prevent SIGSEGV in
fts_query_free_result().

storage/innobase/fts/fts0que.cc

@@ -4019,7 +4019,7 @@ fts_query(
 	if (trx_is_interrupted(trx)) {
 		error = DB_INTERRUPTED;
 		ut_free(lc_query_str);
-		if (result != NULL) {
+		if (*result) {
 			fts_query_free_result(*result);
 		}
 		goto func_exit;

storage/xtradb/fts/fts0que.cc

@@ -4038,7 +4038,7 @@ fts_query(
 	if (trx_is_interrupted(trx)) {
 		error = DB_INTERRUPTED;
 		ut_free(lc_query_str);
-		if (result != NULL) {
+		if (*result) {
 			fts_query_free_result(*result);
 		}
 		goto func_exit;