Joomla Language 303 redirect to better 301 redirect (/plugins/system/languagefilter/languagefilter.php)

languagefilter.php

// redirect if sef does not exists
// around line 226
if (!isset(self::$sefs[$sef]))
{
	// Use the current language sef or the default one
	$sef = isset(self::$lang_codes[$lang_code]) ? self::$lang_codes[$lang_code]->sef : self::$default_sef;
	$uri->setPath($sef . '/' . $path);

	if ($app->getCfg('sef_rewrite')) {
	    // append true for 301 redirect
		$app->redirect($uri->base().$uri->toString(array('path', 'query', 'fragment')),'','',true);
	}
	else {
		$path = $uri->toString(array('path', 'query', 'fragment'));
		// append true for 301 redirect
		$app->redirect($uri->base().'index.php'.($path ? ('/' . $path) : ''),'','',true);
	}
}