assertion failure in dict_table_get_nth_col() after INSTANT DROP COLUMN

CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;

ALTER TABLE t1 ADD COLUMN (b INT, c INT, d INT, e INT NOT NULL DEFAULT 0);

ALTER TABLE t1 ADD UNIQUE INDEX(e);

ALTER TABLE t1 DROP b, DROP c, DROP d, DROP e;

DROP TABLE t1;

Version: '10.4.8-MariaDB-debug-log'  socket: '/dev/shm/10.4d/mysql-test/var/tmp/mysqld.1.sock'  port: 16000  Source distribution

mysqld: /mariadb/10.4/storage/innobase/include/dict0dict.ic:370: dict_col_t *dict_table_get_nth_col(const dict_table_t *, ulint): Assertion `pos < table->n_def' failed.

…

#7  0x000055a0e64f112e in dict_table_get_nth_col (table=0x7f81e0176ef8, pos=4) at /mariadb/10.4/storage/innobase/include/dict0dict.ic:370

#8  check_col_exists_in_indexes (table=0x7f81e0176ef8, col_no=4, is_v=<optimized out>, only_committed=<optimized out>) at /mariadb/10.4/storage/innobase/handler/handler0alter.cc:8523

#9  0x000055a0e64f9295 in commit_cache_norebuild (ha_alter_info=<optimized out>, ctx=<optimized out>, altered_table=<optimized out>, table=<optimized out>, trx=0x7f8230f0d390) at /mariadb/10.4/storage/innobase/handler/handler0alter.cc:10296

#10 0x000055a0e64ec8c2 in ha_innobase::commit_inplace_alter_table (this=0x7f81e0177b60, altered_table=0x7f823044cb20, ha_alter_info=0x7f823044c8f8, commit=<optimized out>) at /mariadb/10.4/storage/innobase/handler/handler0alter.cc:11124