### 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)

wc.lpszClassName = L"Engine";
	if (!RegisterClassExW(&wc)) {
		MessageBoxW(nullptr, L"Failed To Register The Window Class.", L"ERROR", MB_OK | MB_ICONEXCLAMATION);
		r_error = ERR_UNAVAILABLE;
		return;
	}
	_register_raw_input_devices(INVALID_WINDOW_ID);
#if defined(VULKAN_ENABLED)
	if (rendering_driver == "vulkan") {
		context_vulkan = memnew(VulkanContextWindows);
		if (context_vulkan->initialize() != OK) {
			memdelete(context_vulkan);
			context_vulkan = nullptr;
			r_error = ERR_UNAVAILABLE;
			return;
		}
	}
#endif
	
#if defined(GLES3_ENABLED)
	if (rendering_driver == "opengl3") {
		GLManager_Windows::ContextType opengl_api_type = GLManager_Windows::GLES_3_0_COMPATIBLE;
		gl_manager = memnew(GLManager_Windows(opengl_api_type));
		if (gl_manager->initialize() != OK) {
			memdelete(gl_manager);
			gl_manager = nullptr;
			r_error = ERR_UNAVAILABLE;
			return;
		}
		RasterizerGLES3::make_current();