### 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(!windows.has(p_window));
	windows[p_window].mpath = p_region;
	_update_window_mouse_passthrough(p_window);
}
void DisplayServerWindows::_update_window_mouse_passthrough(WindowID p_window) {
	ERR_FAIL_COND(!windows.has(p_window));
	if (windows[p_window].mpass || windows[p_window].mpath.size() == 0) {
		SetWindowRgn(windows[p_window].hWnd, nullptr, TRUE);
	} else {
		POINT *points = (POINT *)memalloc(sizeof(POINT) * windows[p_window].mpath.size());
		for (int i = 0; i < windows[p_window].mpath.size(); i++) {
			if (windows[p_window].borderless) {
				points[i].x = windows[p_window].mpath[i].x;
				points[i].y = windows[p_window].mpath[i].y;
			} else {
				points[i].x = windows[p_window].mpath[i].x + GetSystemMetrics(SM_CXSIZEFRAME);
				points[i].y = windows[p_window].mpath[i].y + GetSystemMetrics(SM_CYSIZEFRAME) + GetSystemMetrics(SM_CYCAPTION);
			}
		}
		HRGN region = CreatePolygonRgn(points, windows[p_window].mpath.size(), ALTERNATE);
		SetWindowRgn(windows[p_window].hWnd, region, TRUE);
		DeleteObject(region);
		memfree(points);
	}
}
int DisplayServerWindows::window_get_current_screen(WindowID p_window) const {