Assertion `num_fts_index <= 1' failed in prepare_inplace_alter_table_dict

--source include/have_innodb.inc

CREATE TABLE t1 (a VARCHAR(128), b VARCHAR(128)) ENGINE=InnoDB;

ALTER TABLE t1 ADD FULLTEXT INDEX (a);

ALTER TABLE t1 ADD FULLTEXT INDEX (b);

ALTER TABLE t1 ADD c SERIAL;

# Cleanup

DROP TABLE t1;

mysqld: /data/src/10.3/storage/innobase/handler/handler0alter.cc:5457: bool prepare_inplace_alter_table_dict(Alter_inplace_info*, const TABLE*, const TABLE*, const char*, ulint, ulint, ulint, bool, bool): Assertion `num_fts_index <= 1' failed.

190115  0:07:43 [ERROR] mysqld got signal 6 ;

#7  0x00007ff22435aee2 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6

#8  0x000055ad5e1f6e05 in prepare_inplace_alter_table_dict (ha_alter_info=0x7ff21d69d360, altered_table=0x7ff1c80a7f40, old_table=0x7ff1c806dce0, table_name=0x7ff1c800e66d "t1", flags=33, flags2=94, fts_doc_id_col=3, add_fts_doc_id=true, add_fts_doc_id_idx=true) at /data/src/10.3/storage/innobase/handler/handler0alter.cc:5457

#9  0x000055ad5e1fbc10 in ha_innobase::prepare_inplace_alter_table (this=0x7ff1c800d258, altered_table=0x7ff1c80a7f40, ha_alter_info=0x7ff21d69d360) at /data/src/10.3/storage/innobase/handler/handler0alter.cc:6998

#10 0x000055ad5dea32cd in handler::ha_prepare_inplace_alter_table (this=0x7ff1c800d258, altered_table=0x7ff1c80a7f40, ha_alter_info=0x7ff21d69d360) at /data/src/10.3/sql/handler.cc:4436

#11 0x000055ad5dc79bbc in mysql_inplace_alter_table (thd=0x7ff1c8000b00, table_list=0x7ff1c8014dc0, table=0x7ff1c806dce0, altered_table=0x7ff1c80a7f40, ha_alter_info=0x7ff21d69d360, inplace_supported=HA_ALTER_INPLACE_COPY_LOCK, target_mdl_request=0x7ff21d69d490, alter_ctx=0x7ff21d69e090) at /data/src/10.3/sql/sql_table.cc:7515

#12 0x000055ad5dc7fe42 in mysql_alter_table (thd=0x7ff1c8000b00, new_db=0x7ff1c80051b8, new_name=0x7ff1c8005578, create_info=0x7ff21d69ec80, table_list=0x7ff1c8014dc0, alter_info=0x7ff21d69ebc0, order_num=0, order=0x0, ignore=false) at /data/src/10.3/sql/sql_table.cc:9700

#13 0x000055ad5dd07ccb in Sql_cmd_alter_table::execute (this=0x7ff1c80155e8, thd=0x7ff1c8000b00) at /data/src/10.3/sql/sql_alter.cc:497

#14 0x000055ad5dba9598 in mysql_execute_command (thd=0x7ff1c8000b00) at /data/src/10.3/sql/sql_parse.cc:6285

#15 0x000055ad5dbae669 in mysql_parse (thd=0x7ff1c8000b00, rawbuf=0x7ff1c8014cd8 "ALTER TABLE t1 ADD c SERIAL", length=27, parser_state=0x7ff21d6a05f0, is_com_multi=false, is_next_command=false) at /data/src/10.3/sql/sql_parse.cc:8092

#16 0x000055ad5db9b81d in dispatch_command (command=COM_QUERY, thd=0x7ff1c8000b00, packet=0x7ff1c8161121 "ALTER TABLE t1 ADD c SERIAL", packet_length=27, is_com_multi=false, is_next_command=false) at /data/src/10.3/sql/sql_parse.cc:1851

#17 0x000055ad5db9a241 in do_command (thd=0x7ff1c8000b00) at /data/src/10.3/sql/sql_parse.cc:1396

#18 0x000055ad5dd02256 in do_handle_one_connection (connect=0x55ad6045a050) at /data/src/10.3/sql/sql_connect.cc:1402

#19 0x000055ad5dd01fda in handle_one_connection (arg=0x55ad6045a050) at /data/src/10.3/sql/sql_connect.cc:1308

#20 0x000055ad5e19c8dd in pfs_spawn_thread (arg=0x55ad6049b940) at /data/src/10.3/storage/perfschema/pfs.cc:1862

#21 0x00007ff226031494 in start_thread (arg=0x7ff21d6a1700) at pthread_create.c:333

#22 0x00007ff22441793f in clone () from /lib/x86_64-linux-gnu/libc.so.6

mysqltest: At line 5: query 'ALTER TABLE t1 ADD c SERIAL' failed: 1795: InnoDB presently supports one FULLTEXT index creation at a time