SIGSEGV in spider_db_mbase::append_lock_tables on LOCK TABLES

INSTALL PLUGIN Spider SONAME 'ha_spider.so';

CREATE SERVER srv FOREIGN DATA WRAPPER MYSQL OPTIONS (SOCKET'',DATABASE'',USER'',PASSWORD '');

CREATE TABLE t (a INT) ENGINE=Spider;

CREATE TABLE t2 (b INT) ENGINE=Spider COMMENT='WRAPPER "mysql",srv "srv",TABLE "t"';

LOCK TABLES t AS a READ,t2 AS b LOW_PRIORITY WRITE,t2 AS c WRITE;

DROP TABLE t2;

CREATE TABLE t2 (c INT) ENGINE=Spider COMMENT='WRAPPER "mysql",srv "srv",TABLE "t"';

LOCK TABLES t2 WRITE;

Core was generated by `/test/MD221022-mariadb-10.11.1-linux-x86_64-opt/bin/mysqld --no-defaults --core'.

Program terminated with signal SIGSEGV, Segmentation fault.

#0  spider_db_mbase::append_lock_tables (str=<optimized out>, 

    this=<optimized out>)

    at /test/10.11_opt/storage/spider/spd_db_mysql.cc:3678

3678	    switch (tmp_spider->wide_handler->lock_type)

[Current thread is 1 (Thread 0x154848051700 (LWP 1408423))]

(gdb) bt

#0  spider_db_mbase::append_lock_tables (str=<optimized out>, this=<optimized out>) at /test/10.11_opt/storage/spider/spd_db_mysql.cc:3678

#1  spider_db_mbase::append_lock_tables (this=0x1547a0088b70, str=0x1547a008c730) at /test/10.11_opt/storage/spider/spd_db_mysql.cc:3652

#2  0x00001548389aa92c in spider_mbase_handler::lock_tables (this=0x1547a008c6d0, link_idx=0) at /test/10.11_opt/storage/spider/spd_db_mysql.cc:14578

#3  0x00001548389a1ecb in ha_spider::lock_tables (this=this@entry=0x1547a008a760) at /test/10.11_opt/storage/spider/ha_spider.cc:12214

#4  0x00001548389a2200 in ha_spider::external_lock (this=0x1547a008a760, thd=<optimized out>, lock_type=1) at /test/10.11_opt/storage/spider/ha_spider.cc:921

#5  0x000055bd59af5d78 in handler::ha_external_lock (this=0x1547a008a760, thd=thd@entry=0x1547a0000c58, lock_type=lock_type@entry=1) at /test/10.11_opt/sql/handler.cc:7095

#6  0x000055bd59c0b8f9 in lock_external (count=<optimized out>, tables=0x1547a008a718, thd=0x1547a0000c58) at /test/10.11_opt/sql/lock.cc:396

#7  mysql_lock_tables (thd=thd@entry=0x1547a0000c58, sql_lock=sql_lock@entry=0x1547a008a6e8, flags=flags@entry=0) at /test/10.11_opt/sql/lock.cc:341

#8  0x000055bd59c0c3cf in mysql_lock_tables (thd=thd@entry=0x1547a0000c58, tables=0x1547a00111f8, count=count@entry=1, flags=flags@entry=0) at /test/10.11_opt/sql/lock.cc:304

#9  0x000055bd59836a42 in lock_tables (thd=thd@entry=0x1547a0000c58, tables=tables@entry=0x1547a0010920, count=<optimized out>, flags=flags@entry=0) at /test/10.11_opt/sql/sql_base.cc:5821

#10 0x000055bd598a0a54 in lock_tables_open_and_lock_tables (thd=thd@entry=0x1547a0000c58, tables=<optimized out>) at /test/10.11_opt/sql/sql_parse.cc:2958

#11 0x000055bd598ab643 in mysql_execute_command (thd=0x1547a0000c58, is_called_from_prepared_stmt=<optimized out>) at /test/10.11_opt/sql/sql_parse.cc:5124

#12 0x000055bd59898335 in mysql_parse (rawbuf=<optimized out>, length=<optimized out>, parser_state=<optimized out>, thd=0x1547a0000c58) at /test/10.11_opt/sql/sql_parse.cc:8023

#13 mysql_parse (thd=0x1547a0000c58, rawbuf=<optimized out>, length=<optimized out>, parser_state=<optimized out>) at /test/10.11_opt/sql/sql_parse.cc:7945

#14 0x000055bd598a40ea in dispatch_command (command=COM_QUERY, thd=0x1547a0000c58, packet=<optimized out>, packet_length=<optimized out>, blocking=<optimized out>) at /test/10.11_opt/sql/sql_class.h:1346

#15 0x000055bd598a5ee2 in do_command (thd=0x1547a0000c58, blocking=blocking@entry=true) at /test/10.11_opt/sql/sql_parse.cc:1407

#16 0x000055bd599bffbf in do_handle_one_connection (connect=<optimized out>, connect@entry=0x55bd5d2bdce8, put_in_cache=put_in_cache@entry=true) at /test/10.11_opt/sql/sql_connect.cc:1416

#17 0x000055bd599c029d in handle_one_connection (arg=0x55bd5d2bdce8) at /test/10.11_opt/sql/sql_connect.cc:1318

#18 0x000015485fefe609 in start_thread (arg=<optimized out>) at pthread_create.c:477

#19 0x000015485faea133 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95