allow thumbnail.png to not exist

main.go

@@ -217,14 +217,16 @@ func main() {
 	}
 
 	// scan for thumbnail
+	var thumbnail *yt.Thumbnail
 	thumbnailPath, thumbnailSizeBytes, err := scanner.ScanThumbnail(directory)
 	if err != nil {
 		log.Fatalf("Failed to fetch thumbnail: %v", err)
 		os.Exit(1)
-	}
-	thumbnail := &yt.Thumbnail{
-		Filepath: thumbnailPath,
-		SizeBytes: thumbnailSizeBytes,
+	} else {
+		thumbnail = &yt.Thumbnail{
+			Filepath: thumbnailPath,
+			SizeBytes: thumbnailSizeBytes,
+		}
 	}
 
 	// build video template for upload