### 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)

String id = "SYSTEM\\CurrentControlSet\\Control\\Keyboard Layouts\\" + String::num_int64((int64_t)p_layout, 16, false).lpad(8, "0");
	String ret;
	HKEY hkey;
	WCHAR layout_text[1024];
	memset(layout_text, 0, 1024 * sizeof(WCHAR));
	if (RegOpenKeyExW(HKEY_LOCAL_MACHINE, (LPCWSTR)(id.utf16().get_data()), 0, KEY_QUERY_VALUE, &hkey) != ERROR_SUCCESS) {
		return ret;
	}
	DWORD buffer = 1024;
	DWORD vtype = REG_SZ;
	if (RegQueryValueExW(hkey, L"Layout Text", nullptr, &vtype, (LPBYTE)layout_text, &buffer) == ERROR_SUCCESS) {
		ret = String::utf16((const char16_t *)layout_text);
	}
	RegCloseKey(hkey);
	return ret;
}
String DisplayServerWindows::keyboard_get_layout_name(int p_index) const {