[PS8QA] handle_fatal_signal (sig=11) in ha_innopart::prepare_inplace_alter_table

CREATE DATABASE test;
USE test;
create table t1(a ENUM('','b ')default 'b ');
alter table t1 add key(a);
SET expand_fast_index_creation=1;
ALTER TABLE t1 PARTITION BY KEY(a)PARTITIONS 2;

 Core was generated by `/sda/PS190918-percona-server-8.0.12-1-linux-x86_64-debug/bin/mysqld --no-defaul'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  __pthread_kill (threadid=<optimized out>, signo=11) at ../sysdeps/unix/sysv/linux/pthread_kill.c:57
[Current thread is 1 (Thread 0x7fb04597c700 (LWP 7430))]
(gdb) bt
#0  __pthread_kill (threadid=<optimized out>, signo=11) at ../sysdeps/unix/sysv/linux/pthread_kill.c:57
#1  0x000055ab2e49f431 in my_write_core (sig=11) at /git/PS-8.0.12_dbg/mysys/stacktrace.cc:278
#2  0x000055ab2d1e6933 in handle_fatal_signal (sig=11) at /git/PS-8.0.12_dbg/sql/signal_handler.cc:254
#3  <signal handler called>
#4  0x000055ab2e6f632b in ha_innopart::prepare_inplace_alter_table (this=0x7fb013694028, altered_table=0x7fb0134ca820, 
    ha_alter_info=0x7fb045975a20, old_table_def=0x7fb01347cef8, new_table_def=0x7fb01347d178)
    at /git/PS-8.0.12_dbg/storage/innobase/handler/handler0alter.cc:9824
#5  0x000055ab2d372f7c in handler::ha_prepare_inplace_alter_table (this=0x7fb013694028, altered_table=0x7fb0134ca820, 
    ha_alter_info=0x7fb045975a20, old_table_def=0x7fb01347cef8, new_table_def=0x7fb01347d178)
    at /git/PS-8.0.12_dbg/sql/handler.cc:4791
#6  0x000055ab2d0eae6e in remove_secondary_keys (thd=0x7fb013424000, create_info=0x7fb045979720, table=0x7fb0134ca820, 
    alter_info=0x7fb045979820, table_def=0x7fb01347cef8, altered_table_def=0x7fb01347d178)
    at /git/PS-8.0.12_dbg/sql/sql_table.cc:12851
#7  0x000055ab2d0ef544 in mysql_alter_table (thd=0x7fb013424000, new_db=0x7fb0136365a0 "test", new_name=0x0, 
    create_info=0x7fb045979720, table_list=0x7fb013636018, alter_info=0x7fb045979820) at /git/PS-8.0.12_dbg/sql/sql_table.cc:14316
#8  0x000055ab2d5cc0a8 in Sql_cmd_alter_table::execute (this=0x7fb0136365a8, thd=0x7fb013424000)
    at /git/PS-8.0.12_dbg/sql/sql_alter.cc:350
#9  0x000055ab2d02e5df in mysql_execute_command (thd=0x7fb013424000, first_level=true) at /git/PS-8.0.12_dbg/sql/sql_parse.cc:4417
#10 0x000055ab2d030bdd in mysql_parse (thd=0x7fb013424000, parser_state=0x7fb04597b2a0, update_userstat=false)
    at /git/PS-8.0.12_dbg/sql/sql_parse.cc:5139
#11 0x000055ab2d025d69 in dispatch_command (thd=0x7fb013424000, com_data=0x7fb04597bc70, command=COM_QUERY)
    at /git/PS-8.0.12_dbg/sql/sql_parse.cc:1654
#12 0x000055ab2d024558 in do_command (thd=0x7fb013424000) at /git/PS-8.0.12_dbg/sql/sql_parse.cc:1262
#13 0x000055ab2d1d3156 in handle_connection (arg=0x7fafbcc259d0)
    at /git/PS-8.0.12_dbg/sql/conn_handler/connection_handler_per_thread.cc:317
#14 0x000055ab2e590b76 in pfs_spawn_thread (arg=0x7faff54a1520) at /git/PS-8.0.12_dbg/storage/perfschema/pfs.cc:2836
#15 0x00007fb0475c66db in start_thread (arg=0x7fb04597c700) at pthread_create.c:463
#16 0x00007fb045a9e88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95