Fix: gracefully handle invalid DBus setups

Some systems may have an ncspot binary with enabled MPRIS/DBus support, even
though DBus is not actually running on the system or the session is broken.

ncspot should not panic in such a situation, but handle gracefully instead.

Should help with #1139

src/main.rs

@@ -365,7 +365,7 @@ fn main() -> Result<(), String> {
                     spotify.update_status(state.clone());
 
                     #[cfg(feature = "mpris")]
-                    mpris_manager.update()?;
+                    mpris_manager.update();
 
                     #[cfg(unix)]
                     ipc.publish(&state, queue.get_current());