SIGSEGV in spider_string::length 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 (c INT KEY,b INT UNIQUE) ENGINE=Spider;

CREATE TABLE t2 (c INT,d INT,CONSTRAINT fk FOREIGN KEY(d,c) REFERENCES t (c,d)) ENGINE=Spider COMMENT='WRAPPER "mysql",srv "srv",TABLE "t"';

LOCK TABLES t WRITE,t2 WRITE;

TRUNCATE t2;

LOCK TABLES t2 AS a WRITE;

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

Program terminated with signal SIGSEGV, Segmentation fault.

#0  spider_string::length (this=0x2) at /test/10.11_dbg/sql/sql_string.h:278

278	  inline uint32 length() const { return str_length;}

[Current thread is 1 (Thread 0x14f9d0050700 (LWP 449653))]

(gdb) bt

#0  spider_string::length (this=0x2) at /test/10.11_dbg/sql/sql_string.h:278

#1  0x000014f9a774492a in spider_link_get_key (link_for_hash=0x14f9700c5338, length=0x14f9d004e8f8, not_used=<optimized out>) at /test/10.11_dbg/storage/spider/spd_table.cc:385

#2  0x000055843f6a937c in my_hash_key (first=1 '\001', length=0x14f9d004e8f8, record=<optimized out>, hash=0x14f9700c6008) at /test/10.11_dbg/mysys/hash.c:196

#3  hashcmp (hash=hash@entry=0x14f9700c6008, pos=pos@entry=0x14f9700c60c8, key=key@entry=0x14f970089498 "`test`.`t`", length=length@entry=10) at /test/10.11_dbg/mysys/hash.c:379

#4  0x000055843f6a95aa in my_hash_first_from_hash_value (hash=hash@entry=0x14f9700c6008, hash_value=<optimized out>, key=0x14f970089498 "`test`.`t`", length=length@entry=10, current_record=current_record@entry=0x14f9d004e99c) at /test/10.11_dbg/mysys/hash.c:290

#5  0x000055843f6a95fb in my_hash_search_using_hash_value (hash=hash@entry=0x14f9700c6008, hash_value=<optimized out>, key=<optimized out>, length=length@entry=10) at /test/10.11_dbg/mysys/hash.c:244

#6  0x000014f9a77a2324 in spider_mbase_handler::append_lock_tables_list (this=0x14f970083090, conn=0x14f9700c5398, link_idx=0, appended=0x14f9d004ea1c) at /test/10.11_dbg/storage/spider/spd_db_mysql.cc:13130

#7  0x000014f9a778fa6e in ha_spider::append_lock_tables_list (this=this@entry=0x14f9700b6a80) at /test/10.11_dbg/storage/spider/ha_spider.cc:12081

#8  0x000014f9a778feac in ha_spider::store_lock (this=0x14f9700b6a80, thd=0x14f970000d48, to=0x14f9700b9528, lock_type=TL_WRITE) at /test/10.11_dbg/storage/spider/ha_spider.cc:775

#9  0x000055843f115d40 in get_lock_data (thd=thd@entry=0x14f970000d48, table_ptr=table_ptr@entry=0x14f970013be0, count=count@entry=1, flags=flags@entry=1) at /test/10.11_dbg/sql/sql_string.h:655

#10 0x000055843f116160 in mysql_lock_tables (thd=thd@entry=0x14f970000d48, tables=tables@entry=0x14f970013be0, count=count@entry=1, flags=flags@entry=0) at /test/10.11_dbg/sql/lock.cc:301

#11 0x000055843ec46af1 in lock_tables (thd=thd@entry=0x14f970000d48, tables=0x14f970013308, count=<optimized out>, flags=flags@entry=0) at /test/10.11_dbg/sql/sql_base.cc:5821

#12 0x000055843ecc2240 in lock_tables_open_and_lock_tables (thd=thd@entry=0x14f970000d48, tables=<optimized out>) at /test/10.11_dbg/sql/sql_parse.cc:2958

#13 0x000055843eccdd2e in mysql_execute_command (thd=thd@entry=0x14f970000d48, is_called_from_prepared_stmt=is_called_from_prepared_stmt@entry=false) at /test/10.11_dbg/sql/sql_parse.cc:5124

#14 0x000055843ecb8f90 in mysql_parse (thd=thd@entry=0x14f970000d48, rawbuf=<optimized out>, length=<optimized out>, parser_state=parser_state@entry=0x14f9d004f300) at /test/10.11_dbg/sql/sql_parse.cc:8023

#15 0x000055843ecc64ac in dispatch_command (command=command@entry=COM_QUERY, thd=thd@entry=0x14f970000d48, packet=packet@entry=0x14f97000af09 "LOCK TABLES t2 AS a WRITE", packet_length=packet_length@entry=25, blocking=blocking@entry=true) at /test/10.11_dbg/sql/sql_class.h:1346

#16 0x000055843ecc88f4 in do_command (thd=0x14f970000d48, blocking=blocking@entry=true) at /test/10.11_dbg/sql/sql_parse.cc:1407

#17 0x000055843ee25067 in do_handle_one_connection (connect=<optimized out>, connect@entry=0x5584412ffdd8, put_in_cache=put_in_cache@entry=true) at /test/10.11_dbg/sql/sql_connect.cc:1416

#18 0x000055843ee25536 in handle_one_connection (arg=0x5584412ffdd8) at /test/10.11_dbg/sql/sql_connect.cc:1318

#19 0x000014f9e910a609 in start_thread (arg=<optimized out>) at pthread_create.c:477

#20 0x000014f9e8cf6133 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95