fix unit test.

src/Avalonia.Controls/ApiCompatBaseline.txt

@@ -72,6 +72,4 @@ InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platfor
 MembersMustExist : Member 'public void Avalonia.Platform.IWindowImpl.Resize(Avalonia.Size)' does not exist in the implementation but it does exist in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.IWindowImpl.Resize(Avalonia.Size, Avalonia.Platform.PlatformResizeReason)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.ITrayIconImpl Avalonia.Platform.IWindowingPlatform.CreateTrayIcon()' is present in the implementation but not in the contract.
-Total Issues: 70
-Total Issues: 69
-Total Issues: 66
+Total Issues: 73

tests/Avalonia.Controls.UnitTests/WindowTests.cs

@@ -516,6 +516,8 @@ namespace Avalonia.Controls.UnitTests
 
             var screens = new Mock<IScreenImpl>();
             screens.Setup(x => x.AllScreens).Returns(new Screen[] { screen1.Object, screen2.Object });
+            screens.Setup(x => x.ScreenFromPoint(It.IsAny<PixelPoint>())).Returns(screen1.Object);
+            
 
             var windowImpl = MockWindowingPlatform.CreateWindowMock();
             windowImpl.Setup(x => x.ClientSize).Returns(new Size(800, 480));