### Godot version

Godot Engine v4.0.stable.official.92bee43ad

### System information

Windows 10

### Issue description

The documentation states that passing ```null``` into the image parameter of ```set_custom_mouse_cursor``` will change it back to the system cursor, however I find that it removes the cursor's image entirely, rather than setting it to the system's cursor.


### Steps to reproduce

```var isimage = false
var theimage = load("res://final.png")

func _on_my_button_pressed():
    if isimage == false:
        Input.set_custom_mouse_cursor(theimage, Input.CURSOR_ARROW, Vector2(16,16))
        isimage = true
        
    else:
        Input.set_custom_mouse_cursor(null)
        isimage = false```

When the button is pressed, the cursor is meant to change to the new cursor. When it has been pressed a second time, it changes back to the default cursor. However, upon pressing it a second time, it simply disappears. The cursor becomes visible again when the cursor exits and re-enters the window.

### Minimal reproduction project

[null mouse.zip](https://github.com/godotengine/godot/files/10901969/null.mouse.zip)

int layout_count = GetKeyboardLayoutList(0, nullptr);
	ERR_FAIL_INDEX(p_index, layout_count);
	HKL *layouts = (HKL *)memalloc(layout_count * sizeof(HKL));
	GetKeyboardLayoutList(layout_count, layouts);
	ActivateKeyboardLayout(layouts[p_index], KLF_SETFORPROCESS);
	memfree(layouts);
}
String DisplayServerWindows::keyboard_get_layout_language(int p_index) const {
	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);
	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);
	memfree(layouts);
	return String::utf16((const char16_t *)buf).substr(0, 2);
}
Key DisplayServerWindows::keyboard_get_keycode_from_physical(Key p_keycode) const {