Make CI_Lang::line()'s first parameter mandatory (optional doesn't make sense)
diff --git a/system/core/Lang.php b/system/core/Lang.php
index 3236709..290b38b 100644
--- a/system/core/Lang.php
+++ b/system/core/Lang.php
@@ -166,7 +166,7 @@
 	 * @param	bool	$log_errors	Whether to log an error message if the line is not found
 	 * @return	string	Translation
 	 */
-	public function line($line = '', $log_errors = TRUE)
+	public function line($line, $log_errors = TRUE)
 	{
 		$value = ($line === '' OR ! isset($this->language[$line])) ? FALSE : $this->language[$line];