viewer: force valid sample type

Fixes #2183

app/render/previewautocacher.cpp

@@ -625,9 +625,12 @@ RenderTicketPtr PreviewAutoCacher::RenderAudio(Node *node, ViewerOutput *context
   connect(watcher, &RenderTicketWatcher::Finished, this, &PreviewAutoCacher::AudioRendered);
   running_audio_tasks_.append(watcher);
 
+  AudioParams p = context->GetAudioParams();
+  p.set_format(ViewerOutput::kDefaultSampleFormat);
+
   RenderManager::RenderAudioParams rap(node,
                                        r,
-                                       context->GetAudioParams(),
+                                       p,
                                        RenderMode::kOffline);
 
   rap.generate_waveforms = dynamic_cast<AudioWaveformCache*>(cache);

app/widget/viewer/viewer.cpp

@@ -510,6 +510,8 @@ void ViewerWidget::UpdateAudioProcessor()
     CloseAudioProcessor();
 
     AudioParams ap = GetConnectedNode()->GetAudioParams();
+    ap.set_format(ViewerOutput::kDefaultSampleFormat);
+
     AudioParams packed(OLIVE_CONFIG("AudioOutputSampleRate").toInt(),
                        OLIVE_CONFIG("AudioOutputChannelLayout").toULongLong(),
                        SampleFormat::from_string(OLIVE_CONFIG("AudioOutputSampleFormat").toString().toStdString()));