### 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)

bottom_end_x = struts[11];
								} else {
									left_start_y = 0;
									left_end_y = desktop_rect.size.y;
									right_start_y = 0;
									right_end_y = desktop_rect.size.y;
									top_start_x = 0;
									top_end_x = desktop_rect.size.x;
									bottom_start_x = 0;
									bottom_end_x = desktop_rect.size.x;
								}
								const Point2i &pos = desktop_rect.position;
								const Size2i &size = desktop_rect.size;
								Rect2i left_rect(pos.x, pos.y + left_start_y, left, left_end_y - left_start_y);
								if (left_rect.size.x > 0) {
									Rect2i intersection = rect.intersection(left_rect);
									if (intersection.has_area() && intersection.size.x < rect.size.x) {
										rect.position.x = left_rect.size.x;
										rect.size.x = rect.size.x - intersection.size.x;
									}
								}
								Rect2i right_rect(pos.x + size.x - right, pos.y + right_start_y, right, right_end_y - right_start_y);
								if (right_rect.size.x > 0) {
									Rect2i intersection = rect.intersection(right_rect);
									if (intersection.has_area() && right_rect.size.x < rect.size.x) {
										rect.size.x = intersection.position.x - rect.position.x;
									}
								}
								Rect2i top_rect(pos.x + top_start_x, pos.y, top_end_x - top_start_x, top);
								if (top_rect.size.y > 0) {