Check if there is actually a title

Don't segfault

feed.go

@@ -263,7 +263,7 @@ func getTitle(url string) string {
 }
 
 func traverse(n *html.Node) (string, bool) {
-	if isTitleElement(n) {
+	if isTitleElement(n) && n.FirstChild != nil {
 		return n.FirstChild.Data, true
 	}