### 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_
	ERR_FAIL_COND_V(!windows.has(p_window), WINDOW_MODE_WINDOWED);
	const WindowData &wd = windows[p_window];
	if (wd.fullscreen) {
		if (wd.multiwindow_fs) {
			return WINDOW_MODE_FULLSCREEN;
		} else {
			return WINDOW_MODE_EXCLUSIVE_FULLSCREEN;
		}
	} else if (wd.minimized) {
		return WINDOW_MODE_MINIMIZED;
	} else if (wd.maximized) {
		return WINDOW_MODE_MAXIMIZED;
	} else {
		return WINDOW_MODE_WINDOWED;
	}
}
bool DisplayServerWindows::window_is_maximize_allowed(WindowID p_window) const {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND_V(!windows.has(p_window), false);
	
	return true;
}
void DisplayServerWindows::window_set_flag(WindowFlags p_flag, bool p_enabled, WindowID p_window) {