Server crashes in Explain_aggr_filesort::print_json_members upon SHOW ANALYZE/EXPLAIN FORMAT=JSON

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

--let $conid= `SELECT CONNECTION_ID()`

--let $run=100

while ($run)

{

  send

    SELECT * FROM sys.waits_by_user_by_latency;

  --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

}

# Cleanup

--disconnect con1

#3  <signal handler called>

#4  0x000055882b57378b in append_item_to_str (out=0x7ffa57f67c90, item=0x7ffa4c01df28) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1546

#5  0x000055882b56fa70 in Explain_aggr_filesort::print_json_members (this=0x7ffa4c070680, writer=0x7ffa57f68050, is_analyze=false) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1059

#6  0x000055882b574c03 in Explain_table_access::print_explain_json (this=0x7ffa4c070120, query=0x7ffa4c06da88, writer=0x7ffa57f68050, is_analyze=false) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1736

#7  0x000055882b5701e3 in Explain_basic_join::print_explain_json_interns (this=0x7ffa4c06ffe8, query=0x7ffa4c06da88, writer=0x7ffa57f68050, is_analyze=false) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1115

#8  0x000055882b56f4f2 in Explain_select::print_explain_json (this=0x7ffa4c06ffe8, query=0x7ffa4c06da88, writer=0x7ffa57f68050, is_analyze=false) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:1010

#9  0x000055882b56926c in Explain_query::print_explain_json (this=0x7ffa4c06da88, output=0x7ffa48018448, is_analyze=false, query_time_in_progress_ms=57) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:238

#10 0x000055882b132e3c in LEX::print_explain (this=0x7ffa4c005100, output=0x7ffa48018448, explain_flags=0 '\000', is_analyze=false, is_json_format=true, printed_anything=0x7ffa57f6822f) at /data/src/preview-10.9-explain-gcov/sql/sql_lex.cc:5856

#11 0x000055882b30fdc0 in Show_explain_request::call_in_target_thread (this=0x7ffa57fb2250) at /data/src/preview-10.9-explain-gcov/sql/sql_show.cc:3003

#12 0x000055882b5db21e in Apc_target::process_apc_requests (this=0x7ffa4c0050a8) at /data/src/preview-10.9-explain-gcov/sql/my_apc.cc:222

#13 0x000055882b57da5f in Apc_target::disable (this=0x7ffa4c0050a8) at /data/src/preview-10.9-explain-gcov/sql/my_apc.h:73

#14 0x000055882b5681c5 in Explain_query::~Explain_query (this=0x7ffa4c06da88, __in_chrg=<optimized out>) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:68

#15 0x000055882b57be06 in delete_explain_query (lex=0x7ffa4c005100) at /data/src/preview-10.9-explain-gcov/sql/sql_explain.cc:2584

#16 0x000055882b18ac30 in log_slow_statement (thd=0x7ffa4c000db8) at /data/src/preview-10.9-explain-gcov/sql/sql_parse.cc:2561

#17 0x000055882b189f11 in dispatch_command (command=COM_QUERY, thd=0x7ffa4c000db8, packet=0x7ffa4c00b9a9 "", packet_length=42, blocking=true) at /data/src/preview-10.9-explain-gcov/sql/sql_parse.cc:2427

#18 0x000055882b18350d in do_command (thd=0x7ffa4c000db8, blocking=true) at /data/src/preview-10.9-explain-gcov/sql/sql_parse.cc:1403

#19 0x000055882b4e55db in do_handle_one_connection (connect=0x558830facaf8, put_in_cache=true) at /data/src/preview-10.9-explain-gcov/sql/sql_connect.cc:1418

#20 0x000055882b4e4de2 in handle_one_connection (arg=0x558830facaf8) at /data/src/preview-10.9-explain-gcov/sql/sql_connect.cc:1312

#21 0x000055882bde30cb in pfs_spawn_thread (arg=0x558830facbd8) at /data/src/preview-10.9-explain-gcov/storage/perfschema/pfs.cc:2201

#22 0x00007ffa69b04ea7 in start_thread (arg=<optimized out>) at pthread_create.c:477

#23 0x00007ffa69703def in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95