### Godot version

v4.0.beta17.mono.official [c40020513]

### System information

Windows 11 22H2

### Issue description

If a focused subwindow is destroyed, DisplayServerWindows may still attempt to send mouse motion events to that window, because `last_focused_window` isn't updated until another window is focused.

```
ERROR: Condition "!windows.has(p_window)" is true. Returning: Point2i()
   at: window_get_position (platform/windows/display_server_windows.cpp:999)
```

### Steps to reproduce

Run the MRP, click some non-Godot application window to focus it, then click the "CLOSE" button in the secondary window. This destroys the window without re-focusing the main window, so hovering the mouse over the main window will produce the error message above.

### Minimal reproduction project

[native_windows_hover.zip](https://github.com/godotengine/godot/files/10573386/native_windows_hover.zip)

_THREAD_SAFE_METHOD_
	if (!windows.has(last_focused_window)) {
		return; 
	}
	
	
	String text = p_text.replace("\r\n", "\n").replace("\n", "\r\n"); 
	if (!OpenClipboard(windows[last_focused_window].hWnd)) {
		ERR_FAIL_MSG("Unable to open clipboard.");
	}
	EmptyClipboard();
	Char16String utf16 = text.utf16();
	HGLOBAL mem = GlobalAlloc(GMEM_MOVEABLE, (utf16.length() + 1) * sizeof(WCHAR));
	ERR_FAIL_COND_MSG(mem == nullptr, "Unable to allocate memory for clipboard contents.");
	LPWSTR lptstrCopy = (LPWSTR)GlobalLock(mem);
	memcpy(lptstrCopy, utf16.get_data(), (utf16.length() + 1) * sizeof(WCHAR));
	GlobalUnlock(mem);
	SetClipboardData(CF_UNICODETEXT, mem);
	
	CharString utf8 = text.utf8();
	mem = GlobalAlloc(GMEM_MOVEABLE, utf8.length() + 1);
	ERR_FAIL_COND_MSG(mem == nullptr, "Unable to allocate memory for clipboard contents.");
	LPTSTR ptr = (LPTSTR)GlobalLock(mem);
	memcpy(ptr, utf8.get_data(), utf8.length());
	ptr[utf8.length()] = 0;
	GlobalUnlock(mem);
	SetClipboardData(CF_TEXT, mem);
	CloseClipboard();
}
String DisplayServerWindows::clipboard_get() const {