null checks

src/tracks/playabletrack/notetrack/ui/NoteTrackSliderHandles.cpp

@@ -38,18 +38,24 @@ std::shared_ptr<NoteTrack> VelocitySliderHandle::GetNoteTrack()
 
 float VelocitySliderHandle::GetValue()
 {
+   if (GetNoteTrack())
       return GetNoteTrack()->GetVelocity();
+   else
+      return 0;
 }
 
 UIHandle::Result VelocitySliderHandle::SetValue
 (AudacityProject *pProject, float newValue)
 {
    auto pTrack = GetNoteTrack();
+
+   if (pTrack) {
       pTrack->SetVelocity(newValue);
 
       MixerBoard *const pMixerBoard = pProject->GetMixerBoard();
       if (pMixerBoard)
          pMixerBoard->UpdateVelocity(pTrack.get());
+   }
 
    return RefreshCode::RefreshCell;
 }

src/tracks/playabletrack/wavetrack/ui/WaveTrackSliderHandles.cpp

@@ -35,13 +35,18 @@ std::shared_ptr<WaveTrack> GainSliderHandle::GetWaveTrack()
 
 float GainSliderHandle::GetValue()
 {
+   if (GetWaveTrack())
       return GetWaveTrack()->GetGain();
+   else
+      return 0;
 }
 
 UIHandle::Result GainSliderHandle::SetValue
 (AudacityProject *pProject, float newValue)
 {
    auto pTrack = GetWaveTrack();
+
+   if (pTrack) {
       pTrack->SetGain(newValue);
 
       // Assume linked track is wave or null
@@ -52,6 +57,7 @@ UIHandle::Result GainSliderHandle::SetValue
       MixerBoard *const pMixerBoard = pProject->GetMixerBoard();
       if (pMixerBoard)
          pMixerBoard->UpdateGain(pTrack.get());
+   }
 
    return RefreshCode::RefreshNone;
 }
@@ -112,12 +118,19 @@ std::shared_ptr<WaveTrack> PanSliderHandle::GetWaveTrack()
 
 float PanSliderHandle::GetValue()
 {
+   if (GetWaveTrack())
       return GetWaveTrack()->GetPan();
+   else
+      return 0;
 }
 
 UIHandle::Result PanSliderHandle::SetValue(AudacityProject *pProject, float newValue)
 {
+   using namespace RefreshCode;
+   Result result = RefreshNone;
    auto pTrack = GetWaveTrack();
+
+   if (pTrack) {
 #ifdef EXPERIMENTAL_OUTPUT_DISPLAY
       bool panZero = false;
       panZero = static_cast<WaveTrack*>(mpTrack)->SetPan(newValue);
@@ -134,13 +147,11 @@ UIHandle::Result PanSliderHandle::SetValue(AudacityProject *pProject, float newV
       if (pMixerBoard)
          pMixerBoard->UpdatePan(pTrack.get());
 
-   using namespace RefreshCode;
-   Result result = RefreshNone;
-
 #ifdef EXPERIMENTAL_OUTPUT_DISPLAY
       if(panZero)
          result |= FixScrollbars;
 #endif
+   }
 
    return result;
 }