Fixed LP bug #972943 properly.

The previous patch for the bug (that erroneously identified the bug as
bug 972973 in its comment) was incorrect. 
It turned out that the code that triggered the abort complain reported for
the bug was not needed at all.

sql/item_subselect.cc

@@ -2726,9 +2726,6 @@ bool subselect_union_engine::no_rows()
 void subselect_uniquesubquery_engine::cleanup()
 {
   DBUG_ENTER("subselect_uniquesubquery_engine::cleanup");
-  /* Tell handler we don't need the index anymore */
-  if (tab->table->file && tab->table->file->inited)
-    tab->table->file->ha_index_end();
   DBUG_VOID_RETURN;
 }
 

sql/sql_select.cc

@@ -15116,7 +15116,6 @@ free_tmp_table(THD *thd, TABLE *entry)
     else
       entry->file->ha_delete_table(entry->s->table_name.str);
     delete entry->file;
-    entry->file= 0;
   }
 
   /* free blobs */