add null checks for _parent.

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

@@ -878,7 +878,11 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     _lastPixelSize.Width = (int)fsize.width;
     _lastPixelSize.Height = (int)fsize.height;
     [self updateRenderTarget];
-    _parent->BaseEvents->ScalingChanged([_parent->Window backingScaleFactor]);
+    
+    if(_parent != nullptr)
+    {
+        _parent->BaseEvents->ScalingChanged([_parent->Window backingScaleFactor]);
+    }
     
     [super viewDidChangeBackingProperties];
 }
@@ -924,7 +928,12 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     auto modifiers = [self getModifiers:[event modifierFlags]];
     
     [self becomeFirstResponder];
-    _parent->BaseEvents->RawMouseEvent(type, timestamp, modifiers, point, delta);
+    
+    if(_parent != nullptr)
+    {
+        _parent->BaseEvents->RawMouseEvent(type, timestamp, modifiers, point, delta);
+    }
+    
     [super mouseMoved:event];
 }
 
@@ -1018,7 +1027,10 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     auto timestamp = [event timestamp] * 1000;
     auto modifiers = [self getModifiers:[event modifierFlags]];
      
-    _lastKeyHandled = _parent->BaseEvents->RawKeyEvent(type, timestamp, modifiers, key);
+    if(_parent != nullptr)
+    {
+        _lastKeyHandled = _parent->BaseEvents->RawKeyEvent(type, timestamp, modifiers, key);
+    }
 }
 
 - (BOOL)performKeyEquivalent:(NSEvent *)event
@@ -1105,7 +1117,10 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
 {
     if(!_lastKeyHandled)
     {
-        _lastKeyHandled = _parent->BaseEvents->RawTextInputEvent(0, [string UTF8String]);
+        if(_parent != nullptr)
+        {
+            _lastKeyHandled = _parent->BaseEvents->RawTextInputEvent(0, [string UTF8String]);
+        }
     }
 }
 
@@ -1372,7 +1387,11 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
         
         [NSApp setMenu:_menu];
         
-        _parent->BaseEvents->Activated();
+        if(_parent != nullptr)
+        {
+            _parent->BaseEvents->Activated();
+        }
+        
         [super becomeKeyWindow];
     }
 }
@@ -1449,8 +1468,12 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
 - (void)windowDidMove:(NSNotification *)notification
 {
     AvnPoint position;
-    _parent->GetPosition(&position);
-    _parent->BaseEvents->PositionChanged(position);
+    
+    if(_parent != nullptr)
+    {
+        _parent->GetPosition(&position);
+        _parent->BaseEvents->PositionChanged(position);
+    }
 }
 @end