MDEV-31545 GCC 13 -Wdangling-pointer in execute_show_status()

The pointer was used deep in the call path.

Resolve this by setting the pointer to NULL at the end of
the function.

Tested with gcc-13.3.1 (fc38)

The warning disable 38fe266e can be reverted in 10.6+ on merge.

sql/sql_parse.cc

@@ -6522,9 +6522,11 @@ static bool execute_show_status(THD *thd, TABLE_LIST *all_tables)
   memcpy(&thd->status_var, &old_status_var,
          offsetof(STATUS_VAR, last_cleared_system_status_var));
   mysql_mutex_unlock(&LOCK_status);
+  thd->initial_status_var= NULL;
   return res;
 #ifdef WITH_WSREP
 wsrep_error_label: /* see WSREP_SYNC_WAIT() macro above */
+  thd->initial_status_var= NULL;
   return true;
 #endif /* WITH_WSREP */
 }