### 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)

if (p_main_window) {
		r_style_ex |= WS_EX_APPWINDOW;
		r_style |= WS_VISIBLE;
	}
	if (p_fullscreen || p_borderless) {
		r_style |= WS_POPUP; 
		if (p_fullscreen && p_multiwindow_fs) {
			r_style |= WS_BORDER; 
		}
	} else {
		if (p_resizable) {
			if (p_maximized) {
				r_style = WS_OVERLAPPEDWINDOW | WS_MAXIMIZE;
			} else {
				r_style = WS_OVERLAPPEDWINDOW;
			}
		} else {
			r_style = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX;
		}
	}
	if (p_no_activate_focus) {
		r_style_ex |= WS_EX_TOPMOST | WS_EX_NOACTIVATE;
	}
	if (!p_borderless && !p_no_activate_focus) {
		r_style |= WS_VISIBLE;
	}
	r_style |= WS_CLIPCHILDREN | WS_CLIPSIBLINGS;
	r_style_ex |= WS_EX_ACCEPTFILES;
}
void DisplayServerWindows::_update_window_style(WindowID p_window, bool p_repaint) {