rocksdb.collation test started to fail with a crash

./mtr rocksdb.collation 

TEST                                      RESULT   TIME (ms) or COMMENT

--------------------------------------------------------------------------

worker[1] Using MTR_BUILD_THREAD 300, with reserved ports 16000..16019

rocksdb.collation                        [ fail ]

        Test ended at 2017-03-16 09:14:47

CURRENT_TEST: rocksdb.collation

mysqltest: At line 188: query 'SET GLOBAL rocksdb_strict_collation_exceptions=null' failed: 2013: Lost connection to MySQL server during query

[Thread debugging using libthread_db enabled]

Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Core was generated by `/home/ubuntu/mariadb-10.2-dbg/sql/mysqld --defaults-group-suffix=.1 --defaults-'.

Program terminated with signal SIGSEGV, Segmentation fault.

#0  __pthread_kill (threadid=<optimized out>, signo=11) at ../sysdeps/unix/sysv/linux/pthread_kill.c:62

62      ../sysdeps/unix/sysv/linux/pthread_kill.c: No such file or directory.

[Current thread is 1 (Thread 0x7fdf7f55e300 (LWP 25006))]

#0  __pthread_kill (threadid=<optimized out>, signo=11) at ../sysdeps/unix/sysv/linux/pthread_kill.c:62

#1  0x000055e1097e807b in my_write_core (sig=11) at /home/ubuntu/mariadb-10.2-dbg/mysys/stacktrace.c:477

#2  0x000055e1090600d0 in handle_fatal_signal (sig=11) at /home/ubuntu/mariadb-10.2-dbg/sql/signal_handler.cc:296

#3  <signal handler called>

#4  strlen () at ../sysdeps/x86_64/strlen.S:106

#5  0x000055e1097e2211 in my_strdup (from=0x0, my_flags=0) at /home/ubuntu/mariadb-10.2-dbg/mysys/my_malloc.c:237

#6  0x00007fdf847a7a0a in myrocks::rocksdb_set_collation_exception_list (thd=0x7fdf58000b00, var=0x7fdf84ff6ee0 <myrocks::mysql_sysvar_strict_collation_exceptions>, var_ptr=0x7fdf850048c0 <myrocks::rocksdb_strict_collation_exceptions>, save=0x7fdf580124f8) at /home/ubuntu/mariadb-10.2-dbg/storage/rocksdb/ha_rocksdb.cc:10520

#7  0x000055e108e161f1 in sys_var_pluginvar::global_update (this=0x55e10b207390, thd=0x7fdf58000b00, var=0x7fdf580124d8) at /home/ubuntu/mariadb-10.2-dbg/sql/sql_plugin.cc:3492

#8  0x000055e108d3c97f in sys_var::update (this=0x55e10b207390, thd=0x7fdf58000b00, var=0x7fdf580124d8) at /home/ubuntu/mariadb-10.2-dbg/sql/set_var.cc:208

#9  0x000055e108d3e6fe in set_var::update (this=0x7fdf580124d8, thd=0x7fdf58000b00) at /home/ubuntu/mariadb-10.2-dbg/sql/set_var.cc:825

#10 0x000055e108d3e2e8 in sql_set_variables (thd=0x7fdf58000b00, var_list=0x7fdf58005310, free=true) at /home/ubuntu/mariadb-10.2-dbg/sql/set_var.cc:726

#11 0x000055e108dfb677 in mysql_execute_command (thd=0x7fdf58000b00) at /home/ubuntu/mariadb-10.2-dbg/sql/sql_parse.cc:4797

#12 0x000055e108e0523b in mysql_parse (thd=0x7fdf58000b00, rawbuf=0x7fdf58012348 "SET GLOBAL rocksdb_strict_collation_exceptions=null", length=51, parser_state=0x7fdf7f55ce10, is_com_multi=false, is_next_command=false) at /home/ubuntu/mariadb-10.2-dbg/sql/sql_parse.cc:7860

#13 0x000055e108df3026 in dispatch_command (command=COM_QUERY, thd=0x7fdf58000b00, packet=0x7fdf5818b581 "SET GLOBAL rocksdb_strict_collation_exceptions=null", packet_length=51, is_com_multi=false, is_next_command=false) at /home/ubuntu/mariadb-10.2-dbg/sql/sql_parse.cc:1812

#14 0x000055e108df198f in do_command (thd=0x7fdf58000b00) at /home/ubuntu/mariadb-10.2-dbg/sql/sql_parse.cc:1362

#15 0x000055e108f3a500 in do_handle_one_connection (connect=0x55e10b402a40) at /home/ubuntu/mariadb-10.2-dbg/sql/sql_connect.cc:1354

#16 0x000055e108f3a280 in handle_one_connection (arg=0x55e10b402a40) at /home/ubuntu/mariadb-10.2-dbg/sql/sql_connect.cc:1260

#17 0x000055e10978aa0a in pfs_spawn_thread (arg=0x55e10b40d5e0) at /home/ubuntu/mariadb-10.2-dbg/storage/perfschema/pfs.cc:1862

#18 0x00007fdf8a66f6ba in start_thread (arg=0x7fdf7f55e300) at pthread_create.c:333

#19 0x00007fdf89b0482d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109