### 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)

Key modifiers = p_keycode & KeyModifierMask::MODIFIER_MASK;
	Key keycode_no_mod = (Key)(p_keycode & KeyModifierMask::CODE_MASK);
	if (keycode_no_mod == Key::PRINT ||
			keycode_no_mod == Key::KP_ADD ||
			keycode_no_mod == Key::KP_5 ||
			(keycode_no_mod >= Key::KEY_0 && keycode_no_mod <= Key::KEY_9)) {
		return p_keycode;
	}
	unsigned int scancode = KeyMappingWindows::get_scancode(keycode_no_mod);
	if (scancode == 0) {
		return p_keycode;
	}
	HKL current_layout = GetKeyboardLayout(0);
	UINT vk = MapVirtualKeyEx(scancode, MAPVK_VSC_TO_VK, current_layout);
	if (vk == 0) {
		return p_keycode;
	}
	UINT char_code = MapVirtualKeyEx(vk, MAPVK_VK_TO_CHAR, current_layout) & 0x7FFF;
	
	
	if (char_code >= 32 && char_code <= 127) {
		
		if (char_code == (unsigned int)Key::BRACKETLEFT || char_code == (unsigned int)Key::BRACKETRIGHT) {
			char_code += 32;
		}
		return (Key)(char_code | (unsigned int)modifiers);
	}
	return (Key)(KeyMappingWindows::get_keysym(vk) | modifiers);
}
String _get_full_layout_name_from_registry(HKL p_layout) {