### 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)

return "Windows";
}
void DisplayServerWindows::_set_mouse_mode_impl(MouseMode p_mode) {
	if (windows.has(MAIN_WINDOW_ID) && (p_mode == MOUSE_MODE_CAPTURED || p_mode == MOUSE_MODE_CONFINED || p_mode == MOUSE_MODE_CONFINED_HIDDEN)) {
		
		WindowID window_id = _get_focused_window_or_popup();
		if (!windows.has(window_id)) {
			window_id = MAIN_WINDOW_ID;
		}
		WindowData &wd = windows[window_id];
		RECT clipRect;
		GetClientRect(wd.hWnd, &clipRect);
		ClientToScreen(wd.hWnd, (POINT *)&clipRect.left);
		ClientToScreen(wd.hWnd, (POINT *)&clipRect.right);
		ClipCursor(&clipRect);
		if (p_mode == MOUSE_MODE_CAPTURED) {
			center = window_get_size() / 2;
			POINT pos = { (int)center.x, (int)center.y };
			ClientToScreen(wd.hWnd, &pos);