### 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));
	WindowData &wd = windows[p_window];
	DWORD style = 0;
	DWORD style_ex = 0;
	_get_window_style(p_window == MAIN_WINDOW_ID, wd.fullscreen, wd.multiwindow_fs, wd.borderless, wd.resizable, wd.maximized, wd.no_focus || wd.is_popup, style, style_ex);
	SetWindowLongPtr(wd.hWnd, GWL_STYLE, style);
	SetWindowLongPtr(wd.hWnd, GWL_EXSTYLE, style_ex);
	if (icon.is_valid()) {
		set_icon(icon);
	}
	SetWindowPos(wd.hWnd, wd.always_on_top ? HWND_TOPMOST : HWND_NOTOPMOST, 0, 0, 0, 0, SWP_FRAMECHANGED | SWP_NOMOVE | SWP_NOSIZE | ((wd.no_focus || wd.is_popup) ? SWP_NOACTIVATE : 0));
	if (p_repaint) {
		RECT rect;
		GetWindowRect(wd.hWnd, &rect);
		MoveWindow(wd.hWnd, rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top, TRUE);
	}
}
void DisplayServerWindows::window_set_mode(WindowMode p_mode, WindowID p_window) {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND(!windows.has(p_window));
	WindowData &wd = windows[p_window];
	if (wd.fullscreen && p_mode != WINDOW_MODE_FULLSCREEN && p_mode != WINDOW_MODE_EXCLUSIVE_FULLSCREEN) {
		RECT rect;
		wd.fullscreen = false;
		wd.multiwindow_fs = false;
		wd.maximized = wd.was_maximized;
		if (wd.pre_fs_valid) {
			rect = wd.pre_fs_rect;