Don't post empty articles.

getarticles.go

@@ -211,6 +211,12 @@ func getArticles(feedURL string, max int, noExcerpt bool) (string, error) {
 			return "", err
 		}
 
+		// If the content is empty after html2text (e.g. consisting of an image only)
+		// then stop processing
+		if strings.Replace(mastodonContent, " ", "", -1) == "" {
+			continue
+		}
+
 		output = output + mastodonContent + "\n\n" + cleanURL
 
 		if i > 0 {