minor code cleanup

src/audio_backend/alsa.rs

@@ -16,15 +16,13 @@ impl Open for AlsaSink {
 
 impl Sink for AlsaSink {
     fn start(&mut self) -> io::Result<()> {
-        if self.0.is_some() {
-        } else {
+        if self.0.is_none() {
             match PCM::open(&*self.1,
                                     Stream::Playback, Mode::Blocking,
                                     Format::Signed16, Access::Interleaved,
                                     2, 44100) {
                 Ok(f) => self.0 = Some(f),
                 Err(e) => {
-                    self.0 = None; 
                     error!("Alsa error PCM open {}", e); 
                     return Err(io::Error::new(io::ErrorKind::Other, "Alsa error: PCM open failed"));
                 }