### 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)

int layout_count = GetKeyboardLayoutList(0, nullptr);
	ERR_FAIL_INDEX_V(p_index, layout_count, "");
	HKL *layouts = (HKL *)memalloc(layout_count * sizeof(HKL));
	GetKeyboardLayoutList(layout_count, layouts);
	String ret = _get_full_layout_name_from_registry(layouts[p_index]); 
	if (ret.is_empty()) {
		WCHAR buf[LOCALE_NAME_MAX_LENGTH];
		memset(buf, 0, LOCALE_NAME_MAX_LENGTH * sizeof(WCHAR));
		LCIDToLocaleName(MAKELCID(LOWORD(layouts[p_index]), SORT_DEFAULT), buf, LOCALE_NAME_MAX_LENGTH, 0);
		WCHAR name[1024];
		memset(name, 0, 1024 * sizeof(WCHAR));
		GetLocaleInfoEx(buf, LOCALE_SLOCALIZEDDISPLAYNAME, (LPWSTR)&name, 1024);
		ret = String::utf16((const char16_t *)name);
	}
	memfree(layouts);
	return ret;
}
void DisplayServerWindows::process_events() {