null check uses of CommonTrackPanelCell::FindTrack

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

@@ -151,7 +151,7 @@ HitTestResult NoteTrackControls::HitTest
    const wxRect &rect = evt.rect;
    if (event.ButtonDown() || event.ButtonDClick()) {
       auto track = FindTrack();
-      if (track->GetKind() == Track::Note) {
+      if (track && track->GetKind() == Track::Note) {
          HitTestResult result;
          if (NULL !=
              (result = MuteButtonHandle::HitTest

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

@@ -61,7 +61,7 @@ HitTestResult WaveTrackControls::HitTest
    const wxRect &rect = evt.rect;
    if (event.Button(wxMOUSE_BTN_LEFT)) {
       auto track = FindTrack();
-      if (track->GetKind() == Track::Wave) {
+      if (track && track->GetKind() == Track::Wave) {
          HitTestResult result;
          if (NULL !=
              (result = MuteButtonHandle::HitTest

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

@@ -675,6 +675,8 @@ unsigned WaveTrackVRulerControls::HandleWheelRotation
    evt.event.Skip(false);
 
    Track *const pTrack = FindTrack();
+   if (!pTrack)
+      return RefreshNone;
    wxASSERT(pTrack->GetKind() == Track::Wave);
    auto steps = evt.steps;
 

src/tracks/ui/ButtonHandle.cpp

@@ -38,15 +38,19 @@ HitTestPreview ButtonHandle::HitPreview()
 UIHandle::Result ButtonHandle::Click
 (const TrackPanelMouseEvent &evt, AudacityProject *)
 {
-   const wxMouseEvent &event = evt.event;
    using namespace RefreshCode;
+   auto pTrack = Track::Pointer(
+      static_cast<TrackControls*>(evt.pCell)->FindTrack() );
+   if ( !pTrack )
+      return Cancelled;
+
+   const wxMouseEvent &event = evt.event;
    if (!event.Button(wxMOUSE_BTN_LEFT))
       return Cancelled;
 
    // Come here for left click or double click
    if (mRect.Contains(event.m_x, event.m_y)) {
-      mpTrack = Track::Pointer(
-         static_cast<TrackControls*>(evt.pCell)->FindTrack() );
+      mpTrack = pTrack;
       TrackControls::gCaptureState = mDragCode;
       // Toggle visible button state
       return RefreshCell;

src/tracks/ui/SelectHandle.cpp

@@ -808,9 +808,8 @@ UIHandle::Result SelectHandle::Drag
          return RefreshNone;
    }
 
-   Track *clickedTrack =
-      static_cast<CommonTrackPanelCell*>(evt.pCell)->FindTrack();
-
+   if ( auto clickedTrack =
+       static_cast<CommonTrackPanelCell*>(evt.pCell)->FindTrack() ) {
       // Handle which tracks are selected
       Track *sTrack = pTrack.get();
       Track *eTrack = clickedTrack;
@@ -837,6 +836,7 @@ UIHandle::Result SelectHandle::Drag
 #endif
       
       AdjustSelection(viewInfo, x, mRect.x, clickedTrack);
+   }
 
    return RefreshNone
 

src/tracks/ui/TrackControls.cpp

@@ -203,6 +203,9 @@ unsigned TrackControls::DoContextMenu
    TrackInfo::GetTitleBarRect(rect, buttonRect);
 
    auto track = FindTrack();
+   if (!track)
+      return RefreshCode::RefreshNone;
+
    InitMenuData data{ track, pParent, RefreshCode::RefreshNone };
 
    const auto pTable = &TrackMenuTable::Instance();

src/tracks/ui/TrackSelectHandle.cpp

@@ -96,6 +96,8 @@ UIHandle::Result TrackSelectHandle::Click
 
    TrackControls *const pControls = static_cast<TrackControls*>(evt.pCell);
    Track *const pTrack = pControls->FindTrack();
+   if (!pTrack)
+      return Cancelled;
    TrackPanel *const trackPanel = pProject->GetTrackPanel();
    const bool unsafe = pProject->IsAudioActive();