Comment 3 for bug 890404

==20223== Conditional jump or move depends on uninitialised value(s)
==20223== at 0x8E25B8: mach_write_to_3 (mach0data.ic:129)
==20223== by 0x8E2BA2: mach_write_to_7 (mach0data.ic:359)
==20223== by 0x9550C0: trx_write_roll_ptr (trx0undo.ic:124)
==20223== by 0x931747: row_upd_index_entry_sys_field (row0upd.c:397)
==20223== by 0x969D1B: btr_cur_pessimistic_update (btr0cur.c:2279)
==20223== by 0x934101: row_upd_clust_rec (row0upd.c:1761)
==20223== by 0x9348CF: row_upd_clust_step (row0upd.c:1972)
==20223== by 0x934B03: row_upd (row0upd.c:2050)
==20223== by 0x934DFE: row_upd_step (row0upd.c:2183)
==20223== by 0x91F7BB: row_update_for_mysql (row0mysql.c:1405)
==20223== by 0x8B5591: ha_innobase::update_row(unsigned char const*, unsigned char*) (ha_innodb.cc:5943)
==20223== by 0x7B01C9: handler::ha_update_row(unsigned char const*, unsigned char*) (handler.cc:5053)
==20223== by 0x714C6F: mysql_update(THD*, TABLE_LIST*, List<Item>&, List<Item>&, Item*, unsigned int, st_order*, unsigned long, enum_duplicates, bool) (sql_update.cc:656)
==20223== by 0x658748: mysql_execute_command(THD*, unsigned long long*, unsigned long long*) (sql_parse.cc:3473)
==20223== by 0x661C36: mysql_parse(THD*, char*, unsigned int, char const**, unsigned long long*, char*) (sql_parse.cc:6584)
==20223== by 0x652CBF: dispatch_command(enum_server_command, THD*, char*, unsigned int) (sql_parse.cc:1374)