Fixed an error in the creation of REF access method for materialized

subquery execution, where the the REF buffer format was mistaken to
be in record format instead of key format. The error was that the null
byte for all fields of the record was in the front of the buffer,
and not before each field data.

sql/sql_select.cc

@@ -7925,7 +7925,7 @@ bool TABLE_REF::tmp_table_index_lookup_init(THD *thd,
                                     use that information instead.
                                  */
                                  cur_ref_buff + null_count,
-                                 null_count ? key_buff : 0,
+                                 null_count ? cur_ref_buff : 0,
                                  cur_key_part->length, items[i], value);
     cur_ref_buff+= cur_key_part->store_length;
   }