Add protection when an error occurs while opening the audio device

src/audio/audiolayer.cpp

@@ -96,6 +96,8 @@ AudioLayer::openDevice (int indexIn, int indexOut, int sampleRate, int frameSize
 
   void
 AudioLayer::startStream(void) 
+{
+  if( _CaptureHandle && _PlaybackHandle )
   {
     _talk = true ;
     _debugAlsa(" Start stream\n");
@@ -107,9 +109,12 @@ AudioLayer::startStream(void)
     snd_pcm_prepare( _PlaybackHandle );
     if( err = snd_pcm_start( _PlaybackHandle) < 0 )  _debugAlsa(" Cannot start (%s)\n", snd_strerror(err));
   }
+} 
 
   void
 AudioLayer::stopStream(void) 
+{
+  if( _CaptureHandle && _PlaybackHandle )
   {
     //ost::MutexLock lock( _mutex );
     _debugAlsa(" Stop Stream\n ");
@@ -120,6 +125,7 @@ AudioLayer::stopStream(void)
     snd_pcm_prepare( _PlaybackHandle );
     _urgentBuffer.flush();
   }
+}
 
 void AudioLayer::AlsaCallBack( snd_async_handler_t* pcm_callback )
 {