Mouse.GetPosition throws 'Invalid window handle' when called on UI element loading right after a child window was closed

* .NET Core Version: **.NET SDK, Version: 7.0.101, Commit: bb24aafa11**
* Windows version: **Version 22h2 (OS Build 22621.963)**
* Does the bug reproduce also in WPF for .NET Framework 4.8?: **Yes**
* Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc...)?: **No**

---

**Problem description:**

An attempt to call the `Mouse.GetPosition` method for an UI element in its `Loaded` event handler right after a child window was closed lead to the "System.ComponentModel.Win32Exception: 'Invalid window handle.'" error. This issue occurs only if the mouse pointer is over the UI element that is loaded.

NOTE: You need to enable `Common Language Runtime Exceptions` to see this error.

Please refer to the **Minimal repro** and **Screencast** sections that illustrate the problematic behavior.

---

**Actual behavior:**

```callstack
System.ComponentModel.Win32Exception: 'Invalid window handle.

WindowsBase.dll!MS.Win32.UnsafeNativeMethods.ClientToScreen(System.Runtime.InteropServices.HandleRef hWnd, ref MS.Win32.NativeMethods.POINT pt) Unknown
PresentationCore.dll!MS.Internal.PointUtil.ClientToScreen(System.Windows.Point pointClient, System.Windows.PresentationSource presentationSource) Unknown
PresentationCore.dll!System.Windows.Input.MouseDevice.GetScreenPositionFromSystem() Unknown
PresentationCore.dll!System.Windows.Input.MouseDevice.GetScreenPosition() Unknown
PresentationCore.dll!System.Windows.Input.MouseDevice.GetPosition(System.Windows.IInputElement relativeTo) Unknown
PresentationCore.dll!System.Windows.Input.Mouse.GetPosition(System.Windows.IInputElement relativeTo) Unknown
> WpfCore.dll!WpfCore.MainWindow.Border_Loaded(object sender, System.Windows.RoutedEventArgs e) Line 50 C#
PresentationCore.dll!System.Windows.RoutedEventHandlerInfo.InvokeHandler(object target, System.Windows.RoutedEventArgs routedEventArgs) Unknown
PresentationCore.dll!System.Windows.EventRoute.InvokeHandlersImpl(object source, System.Windows.RoutedEventArgs args, bool reRaised) Unknown
PresentationCore.dll!System.Windows.UIElement.RaiseEventImpl(System.Windows.DependencyObject sender, System.Windows.RoutedEventArgs args) Unknown
PresentationCore.dll!System.Windows.UIElement.RaiseEvent(System.Windows.RoutedEventArgs e) Unknown
PresentationFramework.dll!System.Windows.BroadcastEventHelper.BroadcastEvent(System.Windows.DependencyObject root, System.Windows.RoutedEvent routedEvent) Unknown
PresentationFramework.dll!System.Windows.BroadcastEventHelper.BroadcastLoadedEvent(object root) Unknown
PresentationCore.dll!System.Windows.Media.MediaContext.FireLoadedPendingCallbacks() Unknown
PresentationCore.dll!System.Windows.Media.MediaContext.FireInvokeOnRenderCallbacks() Unknown
PresentationCore.dll!System.Windows.Media.MediaContext.RenderMessageHandlerCore(object resizedCompositionTarget) Unknown
PresentationCore.dll!System.Windows.Media.MediaContext.RenderMessageHandler(object resizedCompositionTarget) Unknown
WindowsBase.dll!System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate callback, object args, int numArgs) Unknown
WindowsBase.dll!System.Windows.Threading.ExceptionWrapper.TryCatchWhen(object source, System.Delegate callback, object args, int numArgs, System.Delegate catchHandler) Unknown
WindowsBase.dll!System.Windows.Threading.DispatcherOperation.InvokeImpl() Unknown
WindowsBase.dll!System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(object state) Unknown
WindowsBase.dll!MS.Internal.CulturePreservingExecutionContext.CallbackWrapper(object obj) Unknown
System.Private.CoreLib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) Unknown
System.Private.CoreLib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) Unknown
WindowsBase.dll!MS.Internal.CulturePreservingExecutionContext.Run(MS.Internal.CulturePreservingExecutionContext executionContext, System.Threading.ContextCallback callback, object state) Unknown
WindowsBase.dll!System.Windows.Threading.DispatcherOperation.Invoke() Unknown
WindowsBase.dll!System.Windows.Threading.Dispatcher.ProcessQueue() Unknown
WindowsBase.dll!System.Windows.Threading.Dispatcher.WndProcHook(System.IntPtr hwnd, int msg, System.IntPtr wParam, System.IntPtr lParam, ref bool handled) Unknown
WindowsBase.dll!MS.Win32.HwndWrapper.WndProc(System.IntPtr hwnd, int msg, System.IntPtr wParam, System.IntPtr lParam, ref bool handled) Unknown
WindowsBase.dll!MS.Win32.HwndSubclass.DispatcherCallbackOperation(object o) Unknown
WindowsBase.dll!System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate callback, object args, int numArgs) Unknown
WindowsBase.dll!System.Windows.Threading.ExceptionWrapper.TryCatchWhen(object source, System.Delegate callback, object args, int numArgs, System.Delegate catchHandler) Unknown
WindowsBase.dll!System.Windows.Threading.Dispatcher.LegacyInvokeImpl(System.Windows.Threading.DispatcherPriority priority, System.TimeSpan timeout, System.Delegate method, object args, int numArgs) Unknown
WindowsBase.dll!MS.Win32.HwndSubclass.SubclassWndProc(System.IntPtr hwnd, int msg, System.IntPtr wParam, System.IntPtr lParam) Unknown
[Native to Managed Transition]
[Managed to Native Transition]
WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame frame) Unknown
WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame frame) Unknown
WindowsBase.dll!System.Windows.Threading.Dispatcher.Run() Unknown
PresentationFramework.dll!System.Windows.Application.RunDispatcher(object ignore) Unknown
PresentationFramework.dll!System.Windows.Application.RunInternal(System.Windows.Window window) Unknown
PresentationFramework.dll!System.Windows.Application.Run() Unknown
WpfCore.dll!WpfCore.App.Main() Unknown
```

---

**Expected behavior:**

The `Mouse.GetPosition` method should return a correct Point value.

---

**Minimal repro:** [dxSample.zip](https://github.com/dotnet/wpf/files/10286316/dxSample.zip)
**Screencast:** [screencast.mp4](https://user-images.githubusercontent.com/31204429/209119622-62c5a6d2-d52d-4206-b301-ef0c94c2d0f2.mp4)

---

**Steps to reproduce:**

1. Enable showing `Common Language Runtime Exceptions` in your Visual Studio;
2. Run any of projects in the attached project;
3. Click the `Test` button in the MainWindow and **do not move** the mouse pointer anywhere;
4. Click in the button from a child window;

At this moment, an error should occur in the Loaded event handler of the Border element. Please refer to the screencast to see the issue.