assertion mtflush_io != NULL on exit with innodb-use-mtflush

 ( cd mysql-test/ ; ./mtr --mysqld=--innodb-use-mtflush --mem innodb.log_file_name )

Thread 1 (Thread 0x3fff91f5d3a0 (LWP 31777)):

#0  0x00003fff918f1964 in __pthread_kill (threadid=<optimized out>, signo=<optimized out>) at ../sysdeps/unix/sysv/linux/pthread_kill.c:58

#1  0x0000000029349fe8 in my_write_core (sig=<optimized out>) at /home/danielgb/mariadb-server-10.2/mysys/stacktrace.c:477

#2  0x0000000028d070bc in handle_fatal_signal (sig=<optimized out>) at /home/danielgb/mariadb-server-10.2/sql/signal_handler.cc:299

#3  <signal handler called>

#4  0x00003fff9141edb0 in __GI_raise (sig=<optimized out>) at ../sysdeps/unix/sysv/linux/raise.c:54

#5  0x00003fff91421270 in __GI_abort () at abort.c:89

#6  0x0000000028a4e298 in ut_dbg_assertion_failed (expr=0x29494668 "mtflush_io != NULL", file=0x29494620 "/home/danielgb/mariadb-server-10.2/storage/innobase/buf/buf0mtflu.cc", line=<optimized out>) at /home/danielgb/mariadb-server-10.2/storage/innobase/ut/ut0dbg.cc:60

#7  0x000000002910adb0 in buf_mtflu_io_thread_exit () at /home/danielgb/mariadb-server-10.2/storage/innobase/buf/buf0mtflu.cc:402

#8  0x00000000290335f4 in srv_shutdown_all_bg_threads () at /home/danielgb/mariadb-server-10.2/storage/innobase/srv/srv0start.cc:1301

#9  0x00000000290339b4 in srv_init_abort_low (create_new_db=<optimized out>, err=DB_ERROR) at /home/danielgb/mariadb-server-10.2/storage/innobase/srv/srv0start.cc:1370

#10 0x000000002903c620 in innobase_start_or_create_for_mysql () at /home/danielgb/mariadb-server-10.2/storage/innobase/srv/srv0start.cc:2604

#11 0x0000000028ef9c54 in innobase_init (p=<optimized out>) at /home/danielgb/mariadb-server-10.2/storage/innobase/handler/ha_innodb.cc:4422

#12 0x0000000028d0a918 in ha_initialize_handlerton (plugin=0x100243a33a0) at /home/danielgb/mariadb-server-10.2/sql/handler.cc:512

#13 0x0000000028b33a5c in plugin_initialize (tmp_root=0x3fffe82001c8, plugin=0x100243a33a0, argc=0x29a12ec8 <remaining_argc>, argv=0x10024219848, options_only=false) at /home/danielgb/mariadb-server-10.2/sql/sql_plugin.cc:1413

#14 0x0000000028b3453c in plugin_init (argc=0x29a12ec8 <remaining_argc>, argv=0x10024219848, flags=<optimized out>) at /home/danielgb/mariadb-server-10.2/sql/sql_plugin.cc:1694

#15 0x0000000028a74980 in init_server_components () at /home/danielgb/mariadb-server-10.2/sql/mysqld.cc:5253

#16 0x0000000028a7a960 in mysqld_main (argc=145, argv=0x10024219848) at /home/danielgb/mariadb-server-10.2/sql/mysqld.cc:5845

#17 0x0000000028a52068 in main (argc=<optimized out>, argv=<optimized out>) at /home/danielgb/mariadb-server-10.2/sql/main.cc:25