Assertion `key_info->key_part->field->flags & (1<< 30)' failed in setup_keyinfo_hash upon rebuilding table with index on blob

--source include/have_innodb.inc

CREATE TABLE t1 ( 

  pk INT,

  c CHAR(100),

  b BLOB,

  PRIMARY KEY(pk),

  KEY(c(64)),

  KEY(b,c(64))

) ENGINE=InnoDB;

ALTER TABLE t1 FORCE;

# Cleanup

DROP TABLE t1;

mysqld: /data/src/10.4/sql/table.cc:8985: void setup_keyinfo_hash(KEY*): Assertion `key_info->key_part->field->flags & (1<< 30)' failed.

190224  3:18:33 [ERROR] mysqld got signal 6 ;

#7  0x00007f2110ee4ee2 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6

#8  0x000055abed949167 in setup_keyinfo_hash (key_info=0x7f20b8155bc8) at /data/src/10.4/sql/table.cc:8985

#9  0x000055abed8feb95 in mysql_prepare_alter_table (thd=0x7f20b8000b00, table=0x7f20b800c960, create_info=0x7f2106205cd0, alter_info=0x7f2106205c10, alter_ctx=0x7f21062050e0) at /data/src/10.4/sql/sql_table.cc:8302

#10 0x000055abed902802 in mysql_alter_table (thd=0x7f20b8000b00, new_db=0x7f20b8005290, new_name=0x7f20b8005690, create_info=0x7f2106205cd0, table_list=0x7f20b8015580, alter_info=0x7f2106205c10, order_num=0, order=0x0, ignore=false) at /data/src/10.4/sql/sql_table.cc:9606

#11 0x000055abed991922 in Sql_cmd_alter_table::execute (this=0x7f20b8015c30, thd=0x7f20b8000b00) at /data/src/10.4/sql/sql_alter.cc:499

#12 0x000055abed822aca in mysql_execute_command (thd=0x7f20b8000b00) at /data/src/10.4/sql/sql_parse.cc:6346

#13 0x000055abed827c72 in mysql_parse (thd=0x7f20b8000b00, rawbuf=0x7f20b80154a8 "ALTER TABLE t1 FORCE", length=20, parser_state=0x7f2106207180, is_com_multi=false, is_next_command=false) at /data/src/10.4/sql/sql_parse.cc:8157

#14 0x000055abed813360 in dispatch_command (command=COM_QUERY, thd=0x7f20b8000b00, packet=0x7f20b81a0091 "ALTER TABLE t1 FORCE", packet_length=20, is_com_multi=false, is_next_command=false) at /data/src/10.4/sql/sql_parse.cc:1829

#15 0x000055abed811b34 in do_command (thd=0x7f20b8000b00) at /data/src/10.4/sql/sql_parse.cc:1358

#16 0x000055abed98b837 in do_handle_one_connection (connect=0x55abf0dabdd0) at /data/src/10.4/sql/sql_connect.cc:1399

#17 0x000055abed98b5a8 in handle_one_connection (arg=0x55abf0dabdd0) at /data/src/10.4/sql/sql_connect.cc:1302

#18 0x000055abede82979 in pfs_spawn_thread (arg=0x55abf0df1a90) at /data/src/10.4/storage/perfschema/pfs.cc:1862

#19 0x00007f2112bbb494 in start_thread (arg=0x7f2106208700) at pthread_create.c:333

#20 0x00007f2110fa193f in clone () from /lib/x86_64-linux-gnu/libc.so.6