Merge pull request #2677 from cwensley/curtis/mac-fix-colorize-when-s…

…ize-changed

Mac: Fix crash when setting background color on some controls and size changes to zero

src/Eto.Mac/ColorizeView.cs

@@ -28,14 +28,14 @@ public void Begin(CGRect frame, NSView controlView)
 			var size = controlView.Frame.Size;
 			if (size.Width <= 0 || size.Height <= 0)
 			{
+				_image?.Dispose();
+				_image = null;
 				return;
 			}
 
 			if (_image == null || size != _image.Size)
 			{
-				if (_image != null)
-					_image.Dispose();
-
+				_image?.Dispose();
 				_image = new NSImage(size);
 			}