Avoid notices.

libraries/common_syndication_parser.inc

@@ -384,9 +384,12 @@ function _parser_common_syndication_RSS20_parse($feed_XML) {
     if (!empty($news['author'])) {
       $original_author = "{$news['author']}";
     }
-    else {
+    elseif (isset($dc["creator"])) {
       $original_author = (string)$dc["creator"];
     }
+    else {
+      $original_author = NULL;
+    }
 
     if (!empty($news['link'])) {
       $original_url = "{$news['link']}";