MDEV-13715 Server crashes in ha_partition::engine_name

This happened when trying to PARTITION a SEQUENCE table
Problem was that wrong function was used to get engine name
Signed-off-by: Monty <monty@mariadb.org>

mysql-test/suite/sql_sequence/partition.result

+#
+# MDEV-13715 ha_partition::engine_name() segfault fix
+#
+create sequence s;
+alter table s partition by hash(start_value) partitions 2;
+ERROR HY000: Table storage engine 'partition' does not support the create option 'SEQUENCE'
+drop sequence s;

mysql-test/suite/sql_sequence/partition.test

+--source include/have_partition.inc
+--source include/have_sequence.inc
+
+--echo #
+--echo # MDEV-13715 ha_partition::engine_name() segfault fix
+--echo #
+
+create sequence s;
+--error ER_ILLEGAL_HA_CREATE_OPTION
+alter table s partition by hash(start_value) partitions 2;
+drop sequence s;

sql/sql_table.cc

@@ -3311,7 +3311,7 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
   {
     if (!(file->ha_table_flags() & HA_CAN_TABLES_WITHOUT_ROLLBACK))
     {
-      my_error(ER_ILLEGAL_HA_CREATE_OPTION, MYF(0), file->engine_name()->str,
+      my_error(ER_ILLEGAL_HA_CREATE_OPTION, MYF(0), file->table_type(),
                "SEQUENCE");
       DBUG_RETURN(TRUE);
     }