Server crashes in ha_connect::create upon DROP INDEX with alter_algorithm=COPY

INSTALL SONAME 'ha_connect';

CREATE TABLE t1 (c INT NOT NULL, KEY idx(c)) ENGINE=CONNECT;

INSERT INTO t1 VALUES (1), (2);

SET alter_algorithm=COPY;

DROP INDEX idx ON t1;

# Cleanup

DROP TABLE t1;

UNINSTALL SONAME 'ha_connect';

#3  <signal handler called>

#4  0x00007f7a83562717 in ha_connect::create (this=0x61d00023beb8, name=0x7f7a83ee8a7f "./test/#sql-alter-27789b-4", table_arg=0x7f7a83ee54a0, create_info=0x7f7a83ee92d0) at /data/src/10.8/storage/connect/ha_connect.cc:6955

#5  0x0000561d3a2030d3 in handler::ha_create (this=0x61d00023beb8, name=0x7f7a83ee8a7f "./test/#sql-alter-27789b-4", form=0x7f7a83ee54a0, info_arg=0x7f7a83ee92d0) at /data/src/10.8/sql/handler.cc:5496

#6  0x0000561d3a207822 in ha_create_table (thd=0x62b00007e218, path=0x7f7a83ee8a7f "./test/#sql-alter-27789b-4", db=0x6290000e6a88 "test", table_name=0x6290000e62f8 "t1", create_info=0x7f7a83ee92d0, frm=0x7f7a83ee6190, skip_frm_file=false) at /data/src/10.8/sql/handler.cc:5964

#7  0x0000561d39c1d3d7 in mysql_alter_table (thd=0x62b00007e218, new_db=0x6290000e6390, new_name=0x6290000e63a0, create_info=0x7f7a83ee92d0, table_list=0x6290000e6378, recreate_info=0x7f7a83ee9080, alter_info=0x7f7a83ee91a0, order_num=0, order=0x0, ignore=false, if_exists=false) at /data/src/10.8/sql/sql_table.cc:10868

#8  0x0000561d3992d6dd in mysql_execute_command (thd=0x62b00007e218, is_called_from_prepared_stmt=false) at /data/src/10.8/sql/sql_parse.cc:4213

#9  0x0000561d399484af in mysql_parse (thd=0x62b00007e218, rawbuf=0x6290000e6238 "DROP INDEX idx ON t1", length=20, parser_state=0x7f7a83ee9a30) at /data/src/10.8/sql/sql_parse.cc:8019

#10 0x0000561d3991e64a in dispatch_command (command=COM_QUERY, thd=0x62b00007e218, packet=0x629000262219 "DROP INDEX idx ON t1", packet_length=20, blocking=true) at /data/src/10.8/sql/sql_parse.cc:1894

#11 0x0000561d3991b3a3 in do_command (thd=0x62b00007e218, blocking=true) at /data/src/10.8/sql/sql_parse.cc:1407

#12 0x0000561d39dbc7b2 in do_handle_one_connection (connect=0x608000002e38, put_in_cache=true) at /data/src/10.8/sql/sql_connect.cc:1416

#13 0x0000561d39dbc173 in handle_one_connection (arg=0x608000002db8) at /data/src/10.8/sql/sql_connect.cc:1318

#14 0x0000561d3a99b276 in pfs_spawn_thread (arg=0x617000005b98) at /data/src/10.8/storage/perfschema/pfs.cc:2201

#15 0x00007f7a8b6a7fd4 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:442

#16 0x00007f7a8b72866c in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81

commit 4c6e8fc572e5a1dbe100f20d471be65aecbb5225

Author: Sergei Golubchik

Date:   Mon Jan 24 18:38:12 2022 +0100

    MDEV-27591 Connect tables (FIX/DOS) don't work with DESC keys - wrong results