A RQG workload generated the following warning:

==21918== Conditional jump or move depends on uninitialised value(s)
==21918== at 0x840ADB8: do_varstring1(Copy_field*) (field_conv.cc:449)
==21918== by 0x833074E: copy_fields(TMP_TABLE_PARAM*) (sql_select.cc:17604)
==21918== by 0x8328D9C: end_send_group(JOIN*, st_join_table*, bool) (sql_select.cc:14557)
==21918== by 0x8326A11: evaluate_join_record(JOIN*, st_join_table*, int) (sql_select.cc:13630)
==21918== by 0x83264EB: sub_select(JOIN*, st_join_table*, bool) (sql_select.cc:13475)
==21918== by 0x83257C2: do_select(JOIN*, List<Item>, st_table, Procedure*) (sql_select.cc:12979)
==21918== by 0x830B21A: JOIN::exec() (sql_select.cc:2392)
==21918== by 0x830B980: mysql_select(THD*, Item**, 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:2602)
==21918== by 0x8303ED0: handle_select(THD*, st_lex*, select_result*, unsigned long) (sql_select.cc:286)
==21918== by 0x829FCD6: execute_sqlcom_select(THD*, TABLE_LIST*) (sql_parse.cc:5102)
==21918== by 0x82967D6: mysql_execute_command(THD*) (sql_parse.cc:2281)
==21918== by 0x82A2247: mysql_parse(THD*, char*, unsigned int, char const**) (sql_parse.cc:6109)
==21918== by 0x8294343: dispatch_command(enum_server_command, THD*, char*, unsigned int) (sql_parse.cc:1209)
==21918== by 0x82937F5: do_command(THD*) (sql_parse.cc:902)
==21918== by 0x82907AB: handle_one_connection (sql_connect.cc:1154)
==21918== by 0xBEA918: start_thread (in /lib/libpthread-2.12.so)