MDEV-27001 Galera crashes when converting table to partition

SQL statments could have table entries added in lexer. This entries
should not invalidate `next_global` member.
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

mysql-test/suite/galera/r/MDEV-27001.result

+connection node_2;
+connection node_1;
+CREATE TABLE t3 (c INT) PARTITION BY RANGE (c) (PARTITION p1 VALUES LESS THAN (1000));
+CREATE TABLE tp2 (c INT);
+ALTER TABLE t3 CONVERT TABLE tp2 TO PARTITION p2 VALUES LESS THAN (2000);
+DROP TABLE t3;

mysql-test/suite/galera/t/MDEV-27001.opt

+--partition=ON
\ No newline at end of file

mysql-test/suite/galera/t/MDEV-27001.test

+--source include/galera_cluster.inc
+--source include/have_innodb.inc
+
+CREATE TABLE t3 (c INT) PARTITION BY RANGE (c) (PARTITION p1 VALUES LESS THAN (1000));
+CREATE TABLE tp2 (c INT);
+ALTER TABLE t3 CONVERT TABLE tp2 TO PARTITION p2 VALUES LESS THAN (2000);
+DROP TABLE t3;
\ No newline at end of file

sql/wsrep_mysqld.cc

@@ -1603,11 +1603,18 @@ wsrep_append_fk_parent_table(THD* thd, TABLE_LIST* tables, wsrep::key_array* key
 {
     bool fail= false;
     TABLE_LIST *table;
+    TABLE_LIST *table_last_in_list;
 
     thd->release_transactional_locks();
     uint counter;
     MDL_savepoint mdl_savepoint= thd->mdl_context.mdl_savepoint();
 
+    for (table_last_in_list= tables;;table_last_in_list= table_last_in_list->next_local) {
+      if (!table_last_in_list->next_local) {
+        break;
+      }
+    }
+
     if (thd->open_temporary_tables(tables) ||
          open_tables(thd, &tables, &counter, MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL))
     {
@@ -1639,11 +1646,19 @@ wsrep_append_fk_parent_table(THD* thd, TABLE_LIST* tables, wsrep::key_array* key
     /* close the table and release MDL locks */
     close_thread_tables(thd);
     thd->mdl_context.rollback_to_savepoint(mdl_savepoint);
+    bool invalidate_next_global= false;
     for (table= tables; table; table= table->next_local)
     {
       table->table= NULL;
-      table->next_global= NULL;
       table->mdl_request.ticket= NULL;
+      // We should invalidate `next_global` only for entries that are added 
+      // in this function
+      if (table == table_last_in_list) {
+        invalidate_next_global= true;
+      }
+      if (invalidate_next_global) {
+        table->next_global= NULL;
+      }
     }
 
     return fail;