Server crashes in hp_is_single_rec upon query with group by and variable assignment

create table t (a text);

insert into t values (0),(0);

select @x := a, count(*) from t group by 1;

drop table t;

#3  <signal handler called>

#4  0x0000559a304522aa in hp_is_single_rec (rec=0x100007fda0c05 <error: Cannot access memory at address 0x100007fda0c05>, visible=20) at /data/bld/testing/bb-blob-monty-debug/storage/heap/heapdef.h:77

#5  0x0000559a30453d0a in hp_materialize_one_blob (info=0x7fda0c240728, chain=0x100007fda0c05 <error: Cannot access memory at address 0x100007fda0c05>, data_len=3693084673) at /data/bld/testing/bb-blob-monty-debug/storage/heap/hp_blob.c:841

#6  0x0000559a3044c725 in hp_key_cmp (keydef=0x7fda0c05d7d0, rec=0x7fda0c05dc08 "\375\001", key=0x7fda280e9f79 "\001", info=0x7fda0c240728) at /data/bld/testing/bb-blob-monty-debug/storage/heap/hp_hash.c:643

#7  0x0000559a3044b063 in hp_search (info=0x7fda0c240728, keyinfo=0x7fda0c05d7d0, key=0x7fda280e9f78 "", nextflag=0) at /data/bld/testing/bb-blob-monty-debug/storage/heap/hp_hash.c:153

#8  0x0000559a3044eb07 in heap_rkey (info=0x7fda0c240728, record=0x7fda0c051720 '\245' <repeats 32 times>, "\377", inx=0, key=0x7fda280e9f78 "", keypart_map=18446744073709551615, find_flag=HA_READ_KEY_EXACT) at /data/bld/testing/bb-blob-monty-debug/storage/heap/hp_rkey.c:64

#9  0x0000559a304477f2 in ha_heap::index_read_map (this=0x7fda0c0511a0, buf=0x7fda0c051720 '\245' <repeats 32 times>, "\377", key=0x7fda280e9f78 "", keypart_map=18446744073709551615, find_flag=HA_READ_KEY_EXACT) at /data/bld/testing/bb-blob-monty-debug/storage/heap/ha_heap.cc:294

#10 0x0000559a3002b92e in handler::ha_index_read_map (this=0x7fda0c0511a0, buf=0x7fda0c051720 '\245' <repeats 32 times>, "\377", key=0x7fda280e9f78 "", keypart_map=18446744073709551615, find_flag=HA_READ_KEY_EXACT) at /data/bld/testing/bb-blob-monty-debug/sql/handler.cc:3670

#11 0x0000559a2fcd1671 in end_update (join=0x7fda0c0173c0, join_tab=0x7fda0c018da8, end_of_records=false) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:24984

#12 0x0000559a2fce6f6a in AGGR_OP::put_record (this=0x7fda0c019b90, end_of_records=false) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:32542

#13 0x0000559a2fcee9fd in AGGR_OP::put_record (this=0x7fda0c019b90) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.h:1103

#14 0x0000559a2fccc500 in sub_select_postjoin_aggr (join=0x7fda0c0173c0, join_tab=0x7fda0c018da8, end_of_records=false) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:22964

#15 0x0000559a2fccd461 in evaluate_join_record (join=0x7fda0c0173c0, join_tab=0x7fda0c0189e0, error=0) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:23500

#16 0x0000559a2fccce12 in sub_select (join=0x7fda0c0173c0, join_tab=0x7fda0c0189e0, end_of_records=false) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:23309

#17 0x0000559a2fccbf08 in do_select (join=0x7fda0c0173c0, procedure=0x0) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:22793

#18 0x0000559a2fc99746 in JOIN::exec_inner (this=0x7fda0c0173c0) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:5023

#19 0x0000559a2fc98836 in JOIN::exec (this=0x7fda0c0173c0) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:4807

#20 0x0000559a2fc9a0df in mysql_select (thd=0x7fda0c000dc8, tables=0x7fda0c016260, fields=..., conds=0x0, og_num=1, order=0x0, group=0x7fda0c016a10, having=0x0, proc_param=0x0, select_options=2164525824, result=0x7fda0c017398, unit=0x7fda0c005298, select_lex=0x7fda0c0158e8) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:5285

#21 0x0000559a2fc881e2 in handle_select (thd=0x7fda0c000dc8, lex=0x7fda0c0051c0, result=0x7fda0c017398, setup_tables_done_option=0) at /data/bld/testing/bb-blob-monty-debug/sql/sql_select.cc:601

#22 0x0000559a2fc29969 in execute_sqlcom_select (thd=0x7fda0c000dc8, all_tables=0x7fda0c016260) at /data/bld/testing/bb-blob-monty-debug/sql/sql_parse.cc:6463

#23 0x0000559a2fc205f6 in mysql_execute_command (thd=0x7fda0c000dc8, is_called_from_prepared_stmt=false) at /data/bld/testing/bb-blob-monty-debug/sql/sql_parse.cc:4042

#24 0x0000559a2fc2e9f1 in mysql_parse (thd=0x7fda0c000dc8, rawbuf=0x7fda0c015830 "select @x := a, count(*) from t group by 1", length=42, parser_state=0x7fda29a0d360) at /data/bld/testing/bb-blob-monty-debug/sql/sql_parse.cc:8223

#25 0x0000559a2fc19cec in dispatch_command (command=COM_QUERY, thd=0x7fda0c000dc8, packet=0x7fda0c00bc29 "", packet_length=42, blocking=true) at /data/bld/testing/bb-blob-monty-debug/sql/sql_parse.cc:1924

#26 0x0000559a2fc1860b in do_command (thd=0x7fda0c000dc8, blocking=true) at /data/bld/testing/bb-blob-monty-debug/sql/sql_parse.cc:1434

#27 0x0000559a2fe173bb in do_handle_one_connection (connect=0x559a59183d28, put_in_cache=true) at /data/bld/testing/bb-blob-monty-debug/sql/sql_connect.cc:1475

#28 0x0000559a2fe1713c in handle_one_connection (arg=0x559a591cc5d8) at /data/bld/testing/bb-blob-monty-debug/sql/sql_connect.cc:1387

#29 0x0000559a30363544 in pfs_spawn_thread (arg=0x559a59183898) at /data/bld/testing/bb-blob-monty-debug/storage/perfschema/pfs.cc:2201

#30 0x00007fda2f8a81c4 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:442

#31 0x00007fda2f92885c in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81