Server crashes in find_role_grant_pair on SHOW GRANTS for an anonymous user

--error 0,ER_CANNOT_USER

drop role r1;

--error 0,ER_CANNOT_USER

create user ''@localhost;

create role r1;

grant r1 to ''@localhost;

--connect (con1,localhost,nonexisting_user,,)

select current_user;

show grants;

#3  <signal handler called>

#4  __stpcpy_ssse3 () at ../sysdeps/x86_64/multiarch/strcpy-ssse3.S:44

#5  0x00000000005b76a6 in find_role_grant_pair (u=0x7f8cac3283c8, h=0x7f8cb39a83d0, r=0x7f8cad734840) at 10.0-base/sql/sql_acl.cc:7538

#6  0x00000000005b78db in show_role_grants (thd=0x7f8cad7eb070, username=0x7f8cad7ec9e0 "", hostname=0x7f8cad7ecd22 "localhost", acl_entry=0x7f8cac3283b0, buff=0x7f8cb39a84d0 "GRANT ", buffsize=1024) at 10.0-base/sql/sql_acl.cc:7573

#7  0x00000000005b72b1 in mysql_show_grants (thd=0x7f8cad7eb070, lex_user=0x7f8cabc33118) at 10.0-base/sql/sql_acl.cc:7470

#8  0x00000000006326cb in mysql_execute_command (thd=0x7f8cad7eb070) at 10.0-base/sql/sql_parse.cc:4026

#9  0x0000000000637c1d in mysql_parse (thd=0x7f8cad7eb070, rawbuf=0x7f8cabc33088 "show grants", length=11, parser_state=0x7f8cb39a94e0) at 10.0-base/sql/sql_parse.cc:6071

#10 0x000000000062a764 in dispatch_command (command=COM_QUERY, thd=0x7f8cad7eb070, packet=0x7f8cad7f0071 "", packet_length=11) at 10.0-base/sql/sql_parse.cc:1105

#11 0x0000000000629c2d in do_command (thd=0x7f8cad7eb070) at 10.0-base/sql/sql_parse.cc:820

#12 0x0000000000746c99 in do_handle_one_connection (thd_arg=0x7f8cad7eb070) at 10.0-base/sql/sql_connect.cc:1266

#13 0x0000000000746a07 in handle_one_connection (arg=0x7f8cad7eb070) at 10.0-base/sql/sql_connect.cc:1181

#14 0x00000000009b225e in pfs_spawn_thread (arg=0x7f8cad749cb0) at 10.0-base/storage/perfschema/pfs.cc:1015

#15 0x00007f8cb2bc2e9a in start_thread (arg=0x7f8cb39aa700) at pthread_create.c:308

#16 0x00007f8cb22f3cbd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112

revision-id: sergii@pisem.net-20131104123739-jx560iqq214zt64s

revno: 3915

branch-nick: 10.0-base

BUILD/compile-pentium-debug-max-no-ndb