Assertion `thd->get_transaction()->is_empty(Transaction_ctx::STMT) || thd->in_sub_stmt || (thd->state_flags & Open_tables_state::BACKUPS_AVAIL)' failed.

2015-11-20T05:08:49.090660Z 2 [ERROR] Column count of mysql.event is wrong. Expected 22, found 20. The table is probably corrupted
mysqld: /git/PS-5.7-Beta_dbg/sql/sql_base.cc:1557: void close_thread_tables(THD*): Assertion `thd->get_transaction()->is_empty(Transaction_ctx::STMT) || thd->in_sub_stmt || (thd->state_flags & Open_tables_state::BACKUPS_AVAIL)' failed.
05:08:49 UTC - mysqld got signal 6 ;

+bt
#0 0x00007f77d3eef771 in __pthread_kill (threadid=<optimized out>, signo=6) at ../nptl/sysdeps/unix/sysv/linux/pthread_kill.c:61
#1 0x00000000017b8e24 in my_write_core (sig=6) at /git/PS-5.7-Beta_dbg/mysys/stacktrace.c:247
#2 0x0000000000e2663f in handle_fatal_signal (sig=6) at /git/PS-5.7-Beta_dbg/sql/signal_handler.cc:223
#3 <signal handler called>
#4 0x00007f77d2af35d7 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#5 0x00007f77d2af4cc8 in __GI_abort () at abort.c:90
#6 0x00007f77d2aec546 in __assert_fail_base (fmt=0x7f77d2c3c128 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=assertion@entry=0x1ec7cd0 "thd->get_transaction()->is_empty(Transaction_ctx::STMT) || thd->in_sub_stmt || (thd->state_flags & Open_tables_state::BACKUPS_AVAIL)", file=file@entry=0x1ec77a8 "/git/PS-5.7-Beta_dbg/sql/sql_base.cc", line=line@entry=1557, function=function@entry=0x1eca080 <close_thread_tables(THD*)::__PRETTY_FUNCTION__> "void close_thread_tables(THD*)") at assert.c:92
#7 0x00007f77d2aec5f2 in __GI___assert_fail (assertion=0x1ec7cd0 "thd->get_transaction()->is_empty(Transaction_ctx::STMT) || thd->in_sub_stmt || (thd->state_flags & Open_tables_state::BACKUPS_AVAIL)", file=0x1ec77a8 "/git/PS-5.7-Beta_dbg/sql/sql_base.cc", line=1557, function=0x1eca080 <close_thread_tables(THD*)::__PRETTY_FUNCTION__> "void close_thread_tables(THD*)") at assert.c:101
#8 0x00000000014245ce in close_thread_tables (thd=0x7f7708019000) at /git/PS-5.7-Beta_dbg/sql/sql_base.cc:1555
#9 0x00000000016c88e0 in Event_db_repository::open_event_table (thd=0x7f7708019000, lock_type=TL_WRITE, table=0x7f77d44e72e0) at /git/PS-5.7-Beta_dbg/sql/event_db_repository.cc:631
#10 0x00000000016c9479 in Event_db_repository::drop_event (this=0x7f77cabff1d0, thd=0x7f7708019000, db=..., name=..., drop_if_exists=true) at /git/PS-5.7-Beta_dbg/sql/event_db_repository.cc:915
#11 0x00000000015edd24 in Events::drop_event (thd=0x7f7708019000, dbname=..., name=..., if_exists=true) at /git/PS-5.7-Beta_dbg/sql/events.cc:587
#12 0x00000000014b3a31 in mysql_execute_command (thd=0x7f7708019000, first_level=true) at /git/PS-5.7-Beta_dbg/sql/sql_parse.cc:3975
#13 0x00000000014b8284 in mysql_parse (thd=0x7f7708019000, parser_state=0x7f77d44e8610) at /git/PS-5.7-Beta_dbg/sql/sql_parse.cc:5665
#14 0x00000000014ad12c in dispatch_command (thd=0x7f7708019000, com_data=0x7f77d44e8db0, command=COM_QUERY) at /git/PS-5.7-Beta_dbg/sql/sql_parse.cc:1304
#15 0x00000000014ac048 in do_command (thd=0x7f7708019000) at /git/PS-5.7-Beta_dbg/sql/sql_parse.cc:867
#16 0x00000000015e2a1b in handle_connection (arg=0x7f77223be280) at /git/PS-5.7-Beta_dbg/sql/conn_handler/connection_handler_per_thread.cc:298
#17 0x00000000017e8208 in pfs_spawn_thread (arg=0x7f77222a9820) at /git/PS-5.7-Beta_dbg/storage/perfschema/pfs.cc:2192
#18 0x00007f77d3eeadf5 in start_thread (arg=0x7f77d44e9700) at pthread_create.c:308
#19 0x00007f77d2bb41ad in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113

# Freshly init'd, clean datadir required before each attempt
# mysqld options required for replay: --maximum-sort_buffer_size=1M --maximum-tmp_table_size=1M --maximum-transaction_alloc_block_size=1M --maximum-transaction_prealloc_size=1M --log-output=none --sql_mode=ONLY_FULL_GROUP_BY --enforce-storage-engine=InnoDB
DROP DATABASE test;CREATE DATABASE test;USE test;
ALTER TABLE mysql.event DROP comment,DROP starts;
drop event if exists event1;