Modified Relay_log_info::cannot_safely_rollback() to handle null pointer

CURRENT_TEST: rpl_gtid.rpl_mts_slave_preserve_commit_order_xa_commit_error_nobinlog
mysqltest: At line 146: Query 'let $_show_slave_status_value= query_get_value($slave_param_statement, $slave_param, 1)' failed.
ERROR 2013 (HY000): Lost connection to MySQL server during query
In included file ./include/wait_for_slave_param.inc: 197
included from ./include/wait_for_slave_sql_error.inc: 55
included from /home/venki/work/ps/6990/mysql-test/suite/rpl_gtid/t/rpl_mts_slave_preserve_commit_order_xa_commit_error_nobinlog.test: 133

Thread 1 (Thread 0x7fe1a02d0700 (LWP 96095)):
#0  __pthread_kill (threadid=<optimized out>, signo=11) at ../sysdeps/unix/sysv/linux/pthread_kill.c:56
#1  0x00005574c12065f7 in my_write_core (sig=11) at /home/venki/work/ps/6990/mysys/stacktrace.cc:306
#2  0x00005574bffcccc5 in handle_fatal_signal (sig=11) at /home/venki/work/ps/6990/sql/signal_handler.cc:172
#3  <signal handler called>
#4  0x00005574bf95918c in Transaction_ctx::THD_TRANS::cannot_safely_rollback (this=0x28) at /home/venki/work/ps/6990/sql/transaction_info.h:121
#5  0x00005574bf9593dd in Transaction_ctx::cannot_safely_rollback (this=0x0, scope=Transaction_ctx::SESSION) at /home/venki/work/ps/6990/sql/transaction_info.h:292
#6  0x00005574c0e9ca46 in Relay_log_info::cannot_safely_rollback (this=0x5574c592b900) at /home/venki/work/ps/6990/sql/rpl_rli.cc:482
#7  0x00005574c0ebedc2 in sql_slave_killed (thd=0x7fe1082ca9d0, rli=0x5574c592b900) at /home/venki/work/ps/6990/sql/rpl_slave.cc:2144
#8  0x00005574c0ed1887 in handle_slave_sql (arg=0x5574c572dee0) at /home/venki/work/ps/6990/sql/rpl_slave.cc:7057
#9  0x00005574c19e90fb in pfs_spawn_thread (arg=0x7fe13403acc0) at /home/venki/work/ps/6990/storage/perfschema/pfs.cc:2855
#10 0x00007fe1d8db0609 in start_thread (arg=<optimized out>) at pthread_create.c:477
#11 0x00007fe1d8518103 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

./mtr rpl_gtid.rpl_mts_slave_preserve_commit_order_xa_commit_error_nobinlog{,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,} --parallel=12 --mem