Add null checks around accessibility host elements

native/Avalonia.Native/src/OSX/AvnView.mm

@@ -943,7 +943,7 @@ static void ConvertTilt(NSPoint tilt, float* xTilt, float* yTilt)
     auto window = (AvnWindow*)[self window];
     auto peer = [window automationPeer];
 
-    if (!peer->IsRootProvider())
+    if (!peer || !peer->IsRootProvider())
         return nil;
 
     auto clientPoint = [window convertPointFromScreen:point];
@@ -980,6 +980,9 @@ static void ConvertTilt(NSPoint tilt, float* xTilt, float* yTilt)
     // of the AvnView.
     auto window = (AvnWindow*)[self window];
     auto peer = [window automationPeer];
+    if (!peer)
+        return;
+
     auto childPeers = peer->GetChildren();
     auto childCount = childPeers != nullptr ? childPeers->GetCount() : 0;
 

native/Avalonia.Native/src/OSX/AvnWindow.mm

@@ -619,7 +619,7 @@
 - (IAvnAutomationPeer* _Nonnull) automationPeer
 {
     auto parent = _parent.tryGet();
-    if (_automationPeer == nullptr)
+    if (_automationPeer == nullptr && parent != nullptr)
     {
         _automationPeer = parent->BaseEvents->GetAutomationPeer();
         _automationNode = new AvnAutomationNode(self);