if source is empty, set it to null in the database

git-svn-id: file:///home/shish/svn/shimmie2/trunk@353 7f39781d-f577-437e-ae19-be835c7a54ca

ext/upload/main.php

@@ -70,6 +70,8 @@ class Upload extends Extension {
 		global $page;
 		global $config;
 		
+		if(empty($source)) $source = null;
+
 		$ok = false;
 		
 		if(!file_exists($file['tmp_name'])) {