Assertion `(length % 4) == 0' failed in my_well_formed_len_utf32

--source include/have_sequence.inc

CREATE TABLE t1 (a INT);

INSERT INTO t1 SELECT seq FROM seq_1_to_163;

SET SESSION character_set_connection= utf32;

SELECT GROUP_CONCAT(@var := a) AS f FROM t1;

# Cleanup

DROP TABLE t1;

mysqld: /data/src/10.1/strings/ctype-ucs2.c:2401: my_well_formed_len_utf32: Assertion `(length % 4) == 0' failed.

200719 17:28:58 [ERROR] mysqld got signal 6 ;

#7  0x00007fcdc32cef12 in __GI___assert_fail (assertion=0x55d8425cf493 "(length % 4) == 0", file=0x55d8425cf320 "/data/src/10.1/strings/ctype-ucs2.c", line=2401, function=0x55d8425cfb40 <__PRETTY_FUNCTION__.11925> "my_well_formed_len_utf32") at assert.c:101

#8  0x000055d84222a53b in my_well_formed_len_utf32 (cs=0x55d842b8e120 <my_charset_utf32_general_ci>, b=0x7fcdba4e686e "", e=0x7fcdba4e6870 "", nchars=1029, error=0x7fcdc4ef8c24) at /data/src/10.1/strings/ctype-ucs2.c:2401

#9  0x000055d841c0d57b in dump_leaf_key (key_arg=0x7fcdba49cb49, count=1, item_arg=0x7fcdba442420) at /data/src/10.1/sql/item_sum.cc:3078

#10 0x000055d841c0e89d in Item_func_group_concat::add (this=0x7fcdba442420) at /data/src/10.1/sql/item_sum.cc:3429

#11 0x000055d841c0ff97 in Aggregator_simple::add (this=0x7fcdba444ef0) at /data/src/10.1/sql/item_sum.h:672

#12 0x000055d841992295 in Item_sum::aggregator_add (this=0x7fcdba442420) at /data/src/10.1/sql/item_sum.h:521

#13 0x000055d84198898a in update_sum_func (func_ptr=0x7fcdba443668) at /data/src/10.1/sql/sql_select.cc:23682

#14 0x000055d84197f7b5 in end_send_group (join=0x7fcdba442fb8, join_tab=0x7fcdba444348, end_of_records=false) at /data/src/10.1/sql/sql_select.cc:19938

#15 0x000055d84197cb2c in evaluate_join_record (join=0x7fcdba442fb8, join_tab=0x7fcdba444000, error=0) at /data/src/10.1/sql/sql_select.cc:18816

#16 0x000055d84197c5cd in sub_select (join=0x7fcdba442fb8, join_tab=0x7fcdba444000, end_of_records=false) at /data/src/10.1/sql/sql_select.cc:18632

#17 0x000055d84197bc75 in do_select (join=0x7fcdba442fb8, fields=0x7fcdba4433b8, table=0x0, procedure=0x0) at /data/src/10.1/sql/sql_select.cc:18248

#18 0x000055d841955886 in JOIN::exec_inner (this=0x7fcdba442fb8) at /data/src/10.1/sql/sql_select.cc:3277

#19 0x000055d841952bb1 in JOIN::exec (this=0x7fcdba442fb8) at /data/src/10.1/sql/sql_select.cc:2564

#20 0x000055d8419560a7 in mysql_select (thd=0x7fcdbc3cb070, rref_pointer_array=0x7fcdbc3cf568, tables=0x7fcdba4428c0, wild_num=0, fields=..., conds=0x0, og_num=0, order=0x0, group=0x0, having=0x0, proc_param=0x0, select_options=2147748608, result=0x7fcdba442f98, unit=0x7fcdbc3cebb8, select_lex=0x7fcdbc3cf2c0) at /data/src/10.1/sql/sql_select.cc:3501

#21 0x000055d84194b816 in handle_select (thd=0x7fcdbc3cb070, lex=0x7fcdbc3ceaf8, result=0x7fcdba442f98, setup_tables_done_option=0) at /data/src/10.1/sql/sql_select.cc:377

#22 0x000055d84191b2d3 in execute_sqlcom_select (thd=0x7fcdbc3cb070, all_tables=0x7fcdba4428c0) at /data/src/10.1/sql/sql_parse.cc:5682

#23 0x000055d841911f9f in mysql_execute_command (thd=0x7fcdbc3cb070) at /data/src/10.1/sql/sql_parse.cc:3029

#24 0x000055d84191ede0 in mysql_parse (thd=0x7fcdbc3cb070, rawbuf=0x7fcdba442088 "SELECT GROUP_CONCAT(@var := a) AS f FROM t1", length=43, parser_state=0x7fcdc4efa5f0) at /data/src/10.1/sql/sql_parse.cc:7200

#25 0x000055d84190dfb7 in dispatch_command (command=COM_QUERY, thd=0x7fcdbc3cb070, packet=0x7fcdbe3ee071 "", packet_length=43) at /data/src/10.1/sql/sql_parse.cc:1491

#26 0x000055d84190ce9c in do_command (thd=0x7fcdbc3cb070) at /data/src/10.1/sql/sql_parse.cc:1123

#27 0x000055d841a4ad3b in do_handle_one_connection (thd_arg=0x7fcdbc3cb070) at /data/src/10.1/sql/sql_connect.cc:1331

#28 0x000055d841a4aa6c in handle_one_connection (arg=0x7fcdbc3cb070) at /data/src/10.1/sql/sql_connect.cc:1242

#29 0x000055d841e68ed4 in pfs_spawn_thread (arg=0x7fcdc2839ef0) at /data/src/10.1/storage/perfschema/pfs.cc:1868

#30 0x00007fcdc4b7d4a4 in start_thread (arg=0x7fcdc4efb700) at pthread_create.c:456

#31 0x00007fcdc338bd0f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97