messages need subjects to link to

mod/message.php

@@ -24,6 +24,9 @@ function message_post(&$a) {
 		return;
 	}
 
+	if(! $strlen($subject))
+		$subject = t('[no subject]');
+
 	$me = q("SELECT * FROM `contact` WHERE `uid` = %d AND `self` = 1 LIMIT 1",
 		intval($_SESSION['uid'])
 	);