Turning Controller Method Argument Mapping into 404

YourController.php

<?php
/**
 * @return void
 */
public function mapRequestArgumentsToControllerArguments() {
	try {
		parent::mapRequestArgumentsToControllerArguments();
	} catch (Tx_Extbase_MVC_Exception_InvalidArgumentValue $exception) {
		$GLOBALS['TSFE']->pageNotFoundAndExit();
	}
}
?>