fixup! SourcesQueueOutput can peek metadata from next source

Author: 0----0

src/queue.rs

@@ -239,7 +239,11 @@ impl SourcesQueueOutput {
             let mut next = self.input.next_sounds.lock().unwrap();
 
             if next.is_empty() {
-                let silence = Box::new(Zero::new_samples(nz!(1), nz!(44100), THRESHOLD)) as Box<_>;
+                let silence = Box::new(Zero::new_samples(
+                    SILENCE_CHANNELS,
+                    SILENCE_SAMPLE_RATE,
+                    THRESHOLD,
+                )) as Box<_>;
                 if self.input.keep_alive_if_empty.load(Ordering::Acquire) {
                     // Play a short silence in order to avoid spinlocking.
                     (silence, None)