### 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)

}
#endif
	mouse_monitor = SetWindowsHookEx(WH_MOUSE, ::MouseProc, nullptr, GetCurrentThreadId());
	Point2i window_position;
	if (p_position != nullptr) {
		window_position = *p_position;
	} else {
		if (p_screen == SCREEN_OF_MAIN_WINDOW) {
			p_screen = SCREEN_PRIMARY;
		}
		window_position = screen_get_position(p_screen) + (screen_get_size(p_screen) - p_resolution) / 2;
	}
	WindowID main_window = _create_window(p_mode, p_vsync_mode, p_flags, Rect2i(window_position, p_resolution));
	ERR_FAIL_COND_MSG(main_window == INVALID_WINDOW_ID, "Failed to create main window.");
	joypad = new JoypadWindows(&windows[MAIN_WINDOW_ID].hWnd);
	for (int i = 0; i < WINDOW_FLAG_MAX; i++) {
		if (p_flags & (1 << i)) {
			window_set_flag(WindowFlags(i), true, main_window);
		}
	}
	show_window(MAIN_WINDOW_ID);
#if defined(VULKAN_ENABLED)
	if (rendering_driver == "vulkan") {
		rendering_device_vulkan = memnew(RenderingDeviceVulkan);
		rendering_device_vulkan->initialize(context_vulkan);
		RendererCompositorRD::make_current();
	}
#endif
	if (!Engine::get_singleton()->is_editor_hint() && !OS::get_singleton()->is_in_low_processor_usage_mode()) {