Server crashes in Explain_table_access::tag_to_json upon SHOW EXPLAIN FORMAT=JSON

--let $run= 100

--connect (con1,localhost,root,,test)

--let $conid= `select connection_id()`

while ($run)

{

  --connection con1

  --send

    SELECT column_name FROM information_schema.columns WHERE table_schema IN ('mysql','information_schema','performance_schema','sys');

  --connection default

  --let $show= 100

  while ($show)

  {

    --error 0,ER_TARGET_NOT_EXPLAINABLE

    eval SHOW EXPLAIN FORMAT=JSON FOR $conid;

    --dec $show

  }

  --connection con1

  --reap

  --dec $run

}

#3  <signal handler called>

#4  0x00005597812f95bb in write_item (writer=0x7f17003ae050, item=0x7f16e4015218) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1534

#5  0x00005597812f9bd1 in Explain_table_access::tag_to_json (this=0x7f16e44610a0, writer=0x7f17003ae050, tag=ET_USING_WHERE) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1592

#6  0x00005597812fc134 in Explain_table_access::print_explain_json (this=0x7f16e44610a0, query=0x7f16e4017198, writer=0x7f17003ae050, is_analyze=false) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1873

#7  0x00005597812f61e3 in Explain_basic_join::print_explain_json_interns (this=0x7f16e4460f68, query=0x7f16e4017198, writer=0x7f17003ae050, is_analyze=false) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1115

#8  0x00005597812f54f2 in Explain_select::print_explain_json (this=0x7f16e4460f68, query=0x7f16e4017198, writer=0x7f17003ae050, is_analyze=false) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1010

#9  0x00005597812ef26c in Explain_query::print_explain_json (this=0x7f16e4017198, output=0x7f16f0018448, is_analyze=false, query_time_in_progress_ms=121) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:238

#10 0x0000559780eb8e3c in LEX::print_explain (this=0x7f16e4005100, output=0x7f16f0018448, explain_flags=0 '\000', is_analyze=false, is_json_format=true, printed_anything=0x7f17003ae22f) at /data/src/preview-10.9-explain-gcov/sql/sql_lex.cc:5856

#11 0x0000559781095dc0 in Show_explain_request::call_in_target_thread (this=0x7f17003f8250) at /data/src/preview-10.9-explain-gcov/sql/sql_show.cc:3003

#12 0x000055978136121e in Apc_target::process_apc_requests (this=0x7f16e40050a8) at /data/src/preview-10.9-explain-gcov/sql/my_apc.cc:222

#13 0x0000559781303a5f in Apc_target::disable (this=0x7f16e40050a8) at /data/src/preview-10.9-explain-gcov/sql/my_apc.h:73

#14 0x00005597812ee1c5 in Explain_query::~Explain_query (this=0x7f16e4017198, __in_chrg=<optimized out>) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:68

#15 0x0000559781301e06 in delete_explain_query (lex=0x7f16e4005100) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:2584

#16 0x0000559780f10c30 in log_slow_statement (thd=0x7f16e4000db8) at /data/src/preview-10.9-explain-gcov/sql/sql_parse.cc:2561

#17 0x0000559780f0ff11 in dispatch_command (command=COM_QUERY, thd=0x7f16e4000db8, packet=0x7f16e400b9a9 "RGUMENT\022", packet_length=130, blocking=true) at /data/src/preview-10.9-explain-gcov/sql/sql_parse.cc:2427

#18 0x0000559780f0950d in do_command (thd=0x7f16e4000db8, blocking=true) at /data/src/preview-10.9-explain-gcov/sql/sql_parse.cc:1403

#19 0x000055978126b5db in do_handle_one_connection (connect=0x55978725daf8, put_in_cache=true) at /data/src/preview-10.9-explain-gcov/sql/sql_connect.cc:1418

#20 0x000055978126ade2 in handle_one_connection (arg=0x55978725daf8) at /data/src/preview-10.9-explain-gcov/sql/sql_connect.cc:1312

#21 0x0000559781b690cb in pfs_spawn_thread (arg=0x55978725dbd8) at /data/src/preview-10.9-explain-gcov/storage/perfschema/pfs.cc:2201

#22 0x00007f1705f19ea7 in start_thread (arg=<optimized out>) at pthread_create.c:477

#23 0x00007f1705b18def in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95