MDEV-25698 SIGSEGV in wsrep_should_replicate_ddl

If temporary internal table is in use `hton` will not be set. Skip check
if DDL should be replicated in this case.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

mysql-test/suite/galera/r/galera_wsrep_mode.result

@@ -10,3 +10,7 @@ Warning	1290	WSREP: wsrep_mode = REQUIRED_PRIMARY_KEY enabled. Table should have
 CREATE TABLE t1 (f1 INTEGER PRIMARY KEY) ENGINE=InnoDB;
 DROP TABLE t1;
 SET GLOBAL wsrep_mode = default;
+SET GLOBAL wsrep_mode = STRICT_REPLICATION;
+CREATE VIEW v AS SELECT * FROM JSON_TABLE ('{"a":0}',"$" COLUMNS (a DECIMAL(1,1) path '$.a')) foo;
+DROP VIEW v;
+SET GLOBAL wsrep_mode = default;

mysql-test/suite/galera/t/galera_wsrep_mode.test

@@ -15,3 +15,11 @@ CREATE TABLE t1 (f1 INTEGER PRIMARY KEY) ENGINE=InnoDB;
 
 DROP TABLE t1;
 SET GLOBAL wsrep_mode = default;
+
+
+# MDEV-25698 SIGSEGV in wsrep_should_replicate_ddl
+
+SET GLOBAL wsrep_mode = STRICT_REPLICATION;
+CREATE VIEW v AS SELECT * FROM JSON_TABLE ('{"a":0}',"$" COLUMNS (a DECIMAL(1,1) path '$.a')) foo;
+DROP VIEW v;
+SET GLOBAL wsrep_mode = default;

sql/wsrep_mysqld.cc

@@ -2229,6 +2229,9 @@ bool wsrep_should_replicate_ddl(THD* thd, const handlerton *hton)
   if (!wsrep_check_mode(WSREP_MODE_STRICT_REPLICATION))
     return true;
 
+  if (!hton)
+    return true;
+
   switch (hton->db_type)
   {
     case DB_TYPE_INNODB: