### 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 (IsIconic(hWnd)) {
					window.minimized = true;
				} else if (IsZoomed(hWnd)) {
					window.maximized = true;
				} else if (window_rect.position == screen_position && window_rect.size == screen_size) {
					window.fullscreen = true;
				}
				if (!window.minimized) {
					window.width = window_client_rect.size.width;
					window.height = window_client_rect.size.height;
					rect_changed = true;
				}
#if defined(VULKAN_ENABLED)
				if (context_vulkan && window.context_created) {
					
					context_vulkan->window_resize(window_id, window.width, window.height);
				}
#endif
			}
			if (!window.minimized && (!(window_pos_params->flags & SWP_NOMOVE) || window_pos_params->flags & SWP_FRAMECHANGED)) {
				window.last_pos = window_client_rect.position;
				rect_changed = true;
			}
			if (rect_changed) {
				if (!window.rect_changed_callback.is_null()) {
					Variant size = Rect2i(window.last_pos.x, window.last_pos.y, window.width, window.height);
					const Variant *args[] = { &size };
					Variant ret;
					Callable::CallError ce;
					window.rect_changed_callback.callp(args, 1, ret, ce);