### 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_
	DisplayServer::WindowID window_id = _get_focused_window_or_popup();
	const WindowData &wd = windows[window_id];
	if (!wd.ime_active) {
		return String();
	}
	String ret;
	int32_t length = ImmGetCompositionStringW(wd.im_himc, GCS_COMPSTR, nullptr, 0);
	wchar_t *string = reinterpret_cast<wchar_t *>(memalloc(length));
	ImmGetCompositionStringW(wd.im_himc, GCS_COMPSTR, string, length);
	ret.parse_utf16((char16_t *)string, length / sizeof(wchar_t));
	memdelete(string);
	return ret;
}
void DisplayServerWindows::window_set_ime_active(const bool p_active, WindowID p_window) {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND(!windows.has(p_window));
	WindowData &wd = windows[p_window];
	if (p_active) {
		wd.ime_active = true;
		ImmAssociateContext(wd.hWnd, wd.im_himc);
		CreateCaret(wd.hWnd, NULL, 1, 1);
		window_set_ime_position(wd.im_position, p_window);
	} else {
		ImmAssociateContext(wd.hWnd, (HIMC)0);
		DestroyCaret();
		wd.ime_active = false;
	}
}
void DisplayServerWindows::window_set_ime_position(const Point2i &p_pos, WindowID p_window) {