Valgrind/MSAN uninitialised value errors upon SHOW PROCEDURE STATUS with condition on Db

CREATE PROCEDURE p() SELECT 1;

SHOW PROCEDURE STATUS WHERE DB = 'test';

DROP PROCEDURE p;

==1922390== Conditional jump or move depends on uninitialised value(s)

==1922390==    at 0x9991C2: Binary_string::c_ptr() (sql_string.h:644)

==1922390==    by 0xBCA2A0: fill_schema_proc(THD*, TABLE_LIST*, Item*) (sql_show.cc:6830)

==1922390==    by 0xBD464A: get_schema_tables_result(JOIN*, enum_schema_table_state) (sql_show.cc:9023)

==1922390==    by 0xB6026C: JOIN::exec_inner() (sql_select.cc:4770)

==1922390==    by 0xB5F5CE: JOIN::exec() (sql_select.cc:4591)

==1922390==    by 0xB60EFF: mysql_select(THD*, TABLE_LIST*, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*) (sql_select.cc:5071)

==1922390==    by 0xB4FF41: handle_select(THD*, LEX*, select_result*, unsigned long) (sql_select.cc:582)

==1922390==    by 0xAF72CB: execute_sqlcom_select(THD*, TABLE_LIST*) (sql_parse.cc:6261)

==1922390==    by 0xAEE4EB: mysql_execute_command(THD*, bool) (sql_parse.cc:3945)

==1922390==    by 0xAFC0E9: mysql_parse(THD*, char*, unsigned int, Parser_state*) (sql_parse.cc:8037)

==1922390==    by 0xAE85A4: dispatch_command(enum_server_command, THD*, char*, unsigned int, bool) (sql_parse.cc:1894)

==1922390==    by 0xAE6F7D: do_command(THD*, bool) (sql_parse.cc:1407)

==1922390==    by 0xCC872D: do_handle_one_connection(CONNECT*, bool) (sql_connect.cc:1418)

==1922390==    by 0xCC83CC: handle_one_connection (sql_connect.cc:1312)

==1922390==    by 0x11E19D1: pfs_spawn_thread (pfs.cc:2201)

==1922390==    by 0x4CE3EA6: start_thread (pthread_create.c:477)

==46489==WARNING: MemorySanitizer: use-of-uninitialized-value

    #0 0x559da3069812 in Binary_string::c_ptr() /home/jenkins/workspace/Source-Build-Test/src/sql/sql_string.h:644:9

    #1 0x559da3069812 in fill_schema_proc(THD*, TABLE_LIST*, Item*) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_show.cc:6830:29

    #2 0x559da307a2ea in get_schema_tables_result(JOIN*, enum_schema_table_state) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_show.cc:9023:11

    #3 0x559da2f257c9 in JOIN::exec_inner() /home/jenkins/workspace/Source-Build-Test/src/sql/sql_select.cc:4770:7

    #4 0x559da2f22b4c in JOIN::exec() /home/jenkins/workspace/Source-Build-Test/src/sql/sql_select.cc:4591:3

    #5 0x559da2e89e72 in mysql_select(THD*, TABLE_LIST*, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_select.cc:5071:9

    #6 0x559da2e88bb8 in handle_select(THD*, LEX*, select_result*, unsigned long) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_select.cc:582:10

    #7 0x559da2d5ccec in execute_sqlcom_select(THD*, TABLE_LIST*) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_parse.cc:6261:12

    #8 0x559da2d369f5 in mysql_execute_command(THD*, bool) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_parse.cc:3945:12

    #9 0x559da2d1d877 in mysql_parse(THD*, char*, unsigned int, Parser_state*) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_parse.cc:8037:18

    #10 0x559da2d11c5d in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_parse.cc:1894:7

    #11 0x559da2d1fc6f in do_command(THD*, bool) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_parse.cc:1407:17

    #12 0x559da33b9fc6 in do_handle_one_connection(CONNECT*, bool) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_connect.cc:1418:11

    #13 0x559da33b9515 in handle_one_connection /home/jenkins/workspace/Source-Build-Test/src/sql/sql_connect.cc:1312:5

    #14 0x559da477000a in pfs_spawn_thread /home/jenkins/workspace/Source-Build-Test/src/storage/perfschema/pfs.cc:2201:3

    #15 0x7f9fc1008608 in start_thread /build/glibc-eX1tMB/glibc-2.31/nptl/pthread_create.c:477:8

    #16 0x7f9fc0d0d292 in clone /build/glibc-eX1tMB/glibc-2.31/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95

  Uninitialized value was created by an allocation of 'keybuf' in the stack frame of function '_Z16fill_schema_procP3THDP10TABLE_LISTP4Item'

    #0 0x559da3068010 in fill_schema_proc(THD*, TABLE_LIST*, Item*) /home/jenkins/workspace/Source-Build-Test/src/sql/sql_show.cc:6763