### 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)

rect = wd.pre_fs_rect;
		} else {
			rect.left = 0;
			rect.right = wd.width;
			rect.top = 0;
			rect.bottom = wd.height;
			wd.pre_fs_valid = true;
		}
		MoveWindow(wd.hWnd, rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top, TRUE);
		if (restore_mouse_trails > 1) {
			SystemParametersInfoA(SPI_SETMOUSETRAILS, restore_mouse_trails, 0, 0);
			restore_mouse_trails = 0;
		}
	} else if (p_mode == WINDOW_MODE_WINDOWED) {
		ShowWindow(wd.hWnd, SW_RESTORE);
		wd.maximized = false;
		wd.minimized = false;
	}
	if (p_mode == WINDOW_MODE_MAXIMIZED) {
		ShowWindow(wd.hWnd, SW_MAXIMIZE);
		wd.maximized = true;
		wd.minimized = false;
	}
	if (p_mode == WINDOW_MODE_MINIMIZED) {
		ShowWindow(wd.hWnd, SW_MINIMIZE);
		wd.maximized = false;
		wd.minimized = true;
	}
	if (p_mode == WINDOW_MODE_EXCLUSIVE_FULLSCREEN) {
		wd.multiwindow_fs = false;