tidy meta tag handling

src/main.rs

@@ -49,7 +49,7 @@ fn yes() -> bool {
 fn handle_mp3(file: DirEntry) {
     let meta = mp3_metadata::read_from_file(file.path()).unwrap();
 
-    for tag in meta.tag {
+    if let Some(tag) = meta.tag {
         println!("----------------------");
         println!("artist: {}", tag.artist.trim());
         println!("album: {}", tag.album.trim());