multicam: ensure node is disconnected when closing

app/widget/multicam/multicamwidget.cpp

@@ -66,7 +66,7 @@ void MulticamWidget::SetMulticamNodeInternal(ViewerOutput *viewer, MultiCamNode
 
 void MulticamWidget::SetMulticamNode(ViewerOutput *viewer, MultiCamNode *n, ClipBlock *clip, const rational &time)
 {
-  if (time == rational::NaN || time == GetTime()) {
+  if (time.isNaN() || time == GetTime()) {
     SetMulticamNodeInternal(viewer, n, clip);
     play_queue_.clear();
   } else {

app/widget/viewer/viewer.cpp

@@ -262,6 +262,9 @@ void ViewerWidget::DisconnectNodeEvent(ViewerOutput *n)
 
   timeline_selected_blocks_.clear();
   node_view_selected_.clear();
+  if (multicam_panel_) {
+    multicam_panel_->SetMulticamNode(nullptr, nullptr, nullptr, rational::NaN);
+  }
 
   CloseAudioProcessor();
   audio_scrub_watchers_.clear();