Tracker: Fix crash when the VirtualDirectoryWindow can't create the PoseView.

Fixes #11859. We may want to show an error message rather than failing
silently, but at least that is better than crashing.

src/kits/tracker/ContainerWindow.cpp

@@ -1200,7 +1200,7 @@ BContainerWindow::SaveState(BMessage& message) const
 bool
 BContainerWindow::StateNeedsSaving() const
 {
-	return fStateNeedsSaving || PoseView()->StateNeedsSaving();
+	return fPoseView != NULL && (fStateNeedsSaving || fPoseView->StateNeedsSaving());
 }
 
 

src/kits/tracker/Tracker.cpp

@@ -1113,6 +1113,12 @@ TTracker::OpenContainerWindow(Model* model, BMessage* originalRefsList,
 
 	if (model != NULL && window->LockLooper()) {
 		window->CreatePoseView(model);
+		if (window->PoseView() == NULL) {
+			// Failed initialization.
+			window->PostMessage(B_QUIT_REQUESTED);
+			window->UnlockLooper();
+			return;
+		}
 		window->UnlockLooper();
 	}
 

src/kits/tracker/VirtualDirectoryWindow.cpp

@@ -76,6 +76,8 @@ void
 VirtualDirectoryWindow::CreatePoseView(Model* model)
 {
 	fPoseView = NewPoseView(model, kListMode);
+	if (fPoseView == NULL)
+		return;
 
 	fBorderedView->GroupLayout()->AddView(fPoseView);
 	fBorderedView->EnableBorderHighlight(false);