make audio encode failure non-fatal so we can run to the end at least

examples/ffmpeg_recorder.rs

@@ -186,7 +186,7 @@ impl MyEmulator {
             self.video_encoder.encode(&vframe, &mut out).unwrap();
         }
         while let Ok(..) = self.audio_filter.get("out").unwrap().sink().frame(&mut aframe) {
-            self.audio_encoder.encode(&aframe, &mut out).unwrap();
+            self.audio_encoder.encode(&aframe, &mut out);//.unwrap();
         }
     }