SIGSEGV in Item_cache_row::store on CASE NEW WHEN in trigger on single-column table

CREATE TABLE t (a INT); 

INSERT INTO t VALUES (1);

DELIMITER $$

CREATE TRIGGER tr BEFORE UPDATE ON t FOR EACH ROW BEGIN CASE NEW WHEN 1 THEN SET @x = 1; ELSE SET @x = 0; END CASE; END $$

DELIMITER ;

UPDATE t SET a = 2; 

Core was generated by `/test/mtest/MDEV-34723/MD301026-mariadb-13.2.0-linux-x86_64-opt/bin/mariadbd --'.

Program terminated with signal SIGSEGV, Segmentation fault.

#0  0x00005f7fa9134467 in Item_cache_row::store (this=0x6e7e9006a560, item=0x6e7e90024330)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/item.cc:11941

11941	    values[i]->store(item->element_index(i));

[Current thread is 1 (LWP 1353025)]

(gdb) bt

#0  0x00005f7fa9134467 in Item_cache_row::store (this=0x6e7e9006a560, item=0x6e7e90024330)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/item.cc:11941

#1  0x00005f7fa8de3b61 in sp_rcontext::set_case_expr (this=0x6e7e9006a440, thd=0x6e7e90000c70, case_expr_id=<optimized out>, case_expr_item_ptr=<optimized out>)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sp_rcontext.cc:830

#2  0x00005f7fa90336a2 in sp_instr_set_case_expr::exec_core (this=0x6e7e900244a0, thd=0x6e7e90024330, nextp=0x767fd00a8394)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sp_instr.cc:3001

#3  0x00005f7fa902e3da in sp_lex_keeper::reset_lex_and_exec_core (this=this@entry=0x6e7e900244d8, thd=thd@entry=0x6e7e90000c70, nextp=nextp@entry=0x767fd00a8394, open_tables=true, instr=instr@entry=0x6e7e900244a0, rerun_the_same_instr=<optimized out>)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sp_instr.cc:420

#4  0x00005f7fa902ea06 in sp_lex_keeper::validate_lex_and_exec_core (this=0x6e7e900244d8, thd=0x6e7e90000c70, nextp=0x767fd00a8394, open_tables=<optimized out>, instr=0x6e7e900244a0)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sp_instr.cc:624

#5  0x00005f7fa8dd75ca in sp_head::execute (this=this@entry=0x6e7e90022e20, thd=thd@entry=0x6e7e90000c70, merge_da_on_success=false)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sp_head.cc:1347

#6  0x00005f7fa8dd8662 in sp_head::execute_trigger (this=0x6e7e90022e20, thd=0x6e7e90000c70, db_name=<optimized out>, table_name=<optimized out>, grant_info=<optimized out>)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sp_head.cc:1863

#7  0x00005f7fa8f51dd6 in Table_triggers_list::process_triggers (this=0x6e7e900565c0, thd=0x6e7e90000c70, event=TRG_EVENT_UPDATE, time_type=<optimized out>, old_row_is_record1=<optimized out>, skip_row_indicator=0x767fd00a8c07, fields_in_update_stmt=0x6e7e90005d78)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_trigger.cc:2918

#8  0x00005f7fa8e18f35 in fill_record_n_invoke_before_triggers (thd=thd@entry=0x6e7e90000c70, table=table@entry=0x6e7e90054ed0, fields=@0x6e7e90005d78: {<base_list> = {<Sql_alloc> = {<No data fields>}, first = 0x6e7e900186c0, last = 0x6e7e900186c0, elements = 1}, <No data fields>}, values=@0x6e7e90006220: {<base_list> = {<Sql_alloc> = {<No data fields>}, first = 0x6e7e900186d0, last = 0x6e7e900186d0, elements = 1}, <No data fields>}, ignore_errors=<optimized out>, event=event@entry=TRG_EVENT_UPDATE, skip_row_indicator=0x767fd00a8c07)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_base.cc:9774

#9  0x00005f7fa8f64551 in Sql_cmd_update::update_single_table (this=this@entry=0x6e7e900186e0, thd=thd@entry=0x6e7e90000c70)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_update.cc:1010

#10 0x00005f7fa8f694b2 in Sql_cmd_update::execute_inner (this=0x6e7e900186e0, thd=0x6e7e90000c70)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_update.cc:3320

#11 0x00005f7fa8efeafb in Sql_cmd_dml::execute (this=0x6e7e900186e0, thd=0x6e7e90000c70)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_select.cc:35131

#12 0x00005f7fa8e865e6 in mysql_execute_command (thd=thd@entry=0x6e7e90000c70, is_called_from_prepared_stmt=false)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_parse.cc:4493

#13 0x00005f7fa8e81942 in mysql_parse (thd=thd@entry=0x6e7e90000c70, rawbuf=<optimized out>, length=<optimized out>, parser_state=parser_state@entry=0x767fd00a9580)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_parse.cc:8005

#14 0x00005f7fa8e7fef8 in dispatch_command (command=command@entry=COM_QUERY, thd=thd@entry=0x6e7e90000c70, packet=packet@entry=0x6e7e90008ea1 "UPDATE t SET a = 2", packet_length=packet_length@entry=18, blocking=true)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_parse.cc:1903

#15 0x00005f7fa8e81db1 in do_command (thd=thd@entry=0x6e7e90000c70, blocking=true)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_parse.cc:1437

#16 0x00005f7fa8faea0d in do_handle_one_connection (connect=<optimized out>, connect@entry=0x5f7fe668bd90, put_in_cache=true)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_connect.cc:1514

#17 0x00005f7fa8fae842 in handle_one_connection (arg=arg@entry=0x5f7fe668bd90)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/sql/sql_connect.cc:1426

#18 0x00005f7fa935d123 in pfs_spawn_thread (arg=0x5f7fe66ac6d0)at /test/mtest/MDEV-34723/bb-MDEV-34723-rucha_opt/storage/perfschema/pfs.cc:2198

#19 0x0000767fd2c9cb84 in start_thread (arg=<optimized out>)at ./nptl/pthread_create.c:447

#20 0x0000767fd2d29ecc in clone3 ()at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:78