Server crashes in Item_null_result::field_type upon SELECT with CHARSET(date) and ROLLUP

CREATE TABLE t (d DATE) ENGINE=MyISAM;

INSERT INTO t VALUES ('2018-12-12');

SELECT CHARSET(d) AS f FROM t GROUP BY d WITH ROLLUP; 

# Cleanup

DROP TABLE t;

#3  <signal handler called>

#4  0x0000555e4ffb80e7 in Item_null_result::field_type (this=0x7f4408445d98) at /data/src/10.1/sql/item.h:2612

#5  0x0000555e4fedfe23 in Item_ref::field_type (this=0x7f4408444368) at /data/src/10.1/sql/item.h:3939

#6  0x0000555e5018c777 in Item::cmp_type (this=0x7f4408444368) at /data/src/10.1/sql/item.cc:658

#7  0x0000555e4fe83287 in Item::charset_for_protocol (this=0x7f4408444368) at /data/src/10.1/sql/item.h:1374

#8  0x0000555e502110cd in Item_func_charset::val_str (this=0x7f4408443268, str=0x7f4412eecdd0) at /data/src/10.1/sql/item_strfunc.cc:3439

#9  0x0000555e5019bc3f in Item::send (this=0x7f4408443268, protocol=0x7f440a0d5600, buffer=0x7f4412eecdd0) at /data/src/10.1/sql/item.cc:6398

#10 0x0000555e4fe80154 in Protocol::send_result_set_row (this=0x7f440a0d5600, row_items=0x7f4408444298) at /data/src/10.1/sql/protocol.cc:914

#11 0x0000555e4fef881a in select_send::send_data (this=0x7f4408443ba0, items=...) at /data/src/10.1/sql/sql_class.cc:2747

#12 0x0000555e4ffb017f in JOIN::rollup_send_data (this=0x7f4408443bc0, idx=0) at /data/src/10.1/sql/sql_select.cc:24032

#13 0x0000555e4ffa5c62 in end_send_group (join=0x7f4408443bc0, join_tab=0x0, end_of_records=true) at /data/src/10.1/sql/sql_select.cc:19769

#14 0x0000555e4ffa213e in do_select (join=0x7f4408443bc0, fields=0x7f4408443fc0, table=0x0, procedure=0x0) at /data/src/10.1/sql/sql_select.cc:18093

#15 0x0000555e4ff7cbac in JOIN::exec_inner (this=0x7f4408443bc0) at /data/src/10.1/sql/sql_select.cc:3275

#16 0x0000555e4ff79e3d in JOIN::exec (this=0x7f4408443bc0) at /data/src/10.1/sql/sql_select.cc:2562

#17 0x0000555e4ff7d3d3 in mysql_select (thd=0x7f440a0d5070, rref_pointer_array=0x7f440a0d9550, tables=0x7f4408443380, wild_num=0, fields=..., conds=0x0, og_num=1, order=0x0, group=0x7f4408443a88, having=0x0, proc_param=0x0, select_options=2147748608, result=0x7f4408443ba0, unit=0x7f440a0d8ba8, select_lex=0x7f440a0d92a8) at /data/src/10.1/sql/sql_select.cc:3499

#18 0x0000555e4ff72a8c in handle_select (thd=0x7f440a0d5070, lex=0x7f440a0d8ae0, result=0x7f4408443ba0, setup_tables_done_option=0) at /data/src/10.1/sql/sql_select.cc:388

#19 0x0000555e4ff4241b in execute_sqlcom_select (thd=0x7f440a0d5070, all_tables=0x7f4408443380) at /data/src/10.1/sql/sql_parse.cc:5948

#20 0x0000555e4ff387ef in mysql_execute_command (thd=0x7f440a0d5070) at /data/src/10.1/sql/sql_parse.cc:2993

#21 0x0000555e4ff4605f in mysql_parse (thd=0x7f440a0d5070, rawbuf=0x7f4408443088 "SELECT CHARSET(d) AS f FROM t GROUP BY d WITH ROLLUP", length=52, parser_state=0x7f4412eee5e0) at /data/src/10.1/sql/sql_parse.cc:7466

#22 0x0000555e4ff348c0 in dispatch_command (command=COM_QUERY, thd=0x7f440a0d5070, packet=0x7f440cbf9071 "", packet_length=52) at /data/src/10.1/sql/sql_parse.cc:1495

#23 0x0000555e4ff33645 in do_command (thd=0x7f440a0d5070) at /data/src/10.1/sql/sql_parse.cc:1124

#24 0x0000555e5006e194 in do_handle_one_connection (thd_arg=0x7f440a0d5070) at /data/src/10.1/sql/sql_connect.cc:1330

#25 0x0000555e5006def8 in handle_one_connection (arg=0x7f440a0d5070) at /data/src/10.1/sql/sql_connect.cc:1242

#26 0x0000555e5042c15e in pfs_spawn_thread (arg=0x7f4410839ef0) at /data/src/10.1/storage/perfschema/pfs.cc:1861

#27 0x00007f4412b6e494 in start_thread (arg=0x7f4412eefb00) at pthread_create.c:333

#28 0x00007f441114293f in clone () from /lib/x86_64-linux-gnu/libc.so.6