A fix for the bug when MyISAM tmp table has to be created in order

to resolve derived table.

Will make a test case for this quite soon.

sql/sql_union.cc

@@ -80,6 +80,7 @@ bool select_union::send_data(List<Item> &values)
   {
     if (create_myisam_from_heap(table, tmp_table_param, info.last_errno, 0))
       return 1;
+    thd->net.report_error=0; // donno why does it work, but it does ...
   }
   return 0;
 }