A fix for a crash in sp.test with -debug-max.

When the joins were not cleaned up before the tables
were closed, a JOIN_TAB still held a pointer to a
meanwhile closed table and tried to close it again
during item cleanup...

sql/sp_head.cc

@@ -681,6 +681,8 @@ sp_head::execute_procedure(THD *thd, List<Item> *args)
 	  nctx->set_oindex(i, static_cast<Item_splocal *>(it)->get_offset());
       }
     }
+    // Clean up the joins before closing the tables.
+    thd->lex->unit.cleanup();
     // Close tables opened for subselect in argument list
     close_thread_tables(thd);