gracefully handle error when showing notification

fixes #265

src/queue.rs

@@ -221,10 +221,9 @@ impl Queue {
             current.replace(index);
             self.spotify.update_track();
             if self.spotify.cfg.notify.unwrap_or(false) {
-                Notification::new()
+                if let Err(e) = Notification::new().summary(&track.to_string()).show() {
-                    .summary(&track.to_string())
+                    error!("error showing notification: {:?}", e);
-                    .show()
+                }
-                    .unwrap();
             }
         }