main.func_json fails in buildbot with crash or valgrind (Conditional jump or move depends on uninitialised value)

main.func_json                           w4 [ fail ]  Found warnings/errors in server log file!

        Test ended at 2016-12-22 11:38:27

line

==15330== Thread 8:

==15330== Conditional jump or move depends on uninitialised value(s)

==15330==    at 0x1120719: my_wildcmp_8bit_impl (ctype-simple.c:926)

==15330==    by 0x1120A05: my_wildcmp_8bit (ctype-simple.c:1010)

==15330==    by 0xAFB321: Item_func_json_search::compare_json_value_wild(st_json_engine_t*, String const*) (item_jsonfunc.cc:2283)

==15330==    by 0xAFBBDA: Item_func_json_search::val_str(String*) (item_jsonfunc.cc:2434)

==15330==    by 0x93CBCC: Item::send(Protocol*, String*) (item.cc:6789)

==15330==    by 0x5D9FC2: Protocol::send_result_set_row(List<Item>*) (protocol.cc:979)

==15330==    by 0x65AA07: select_send::send_data(List<Item>&) (sql_class.cc:2759)

==15330==    by 0x6EA9D8: JOIN::exec_inner() (sql_select.cc:3279)

==15330==    by 0x6EA463: JOIN::exec() (sql_select.cc:3199)

==15330==    by 0x6EB5C5: mysql_select(THD*, TABLE_LIST*, unsigned int, 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:3584)

==15330==    by 0x6E055F: handle_select(THD*, LEX*, select_result*, unsigned long) (sql_select.cc:373)

==15330==    by 0x6AC2D9: execute_sqlcom_select(THD*, TABLE_LIST*) (sql_parse.cc:6399)