### 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)

r_error = ERR_CANT_CREATE;
			ERR_FAIL_MSG("Could not initialize Vulkan");
		}
		driver_found = true;
	}
#endif
	
#if defined(GLES3_ENABLED)
	if (rendering_driver == "opengl3") {
		if (getenv("DRI_PRIME") == nullptr) {
			int use_prime = -1;
			if (getenv("PRIMUS_DISPLAY") ||
					getenv("PRIMUS_libGLd") ||
					getenv("PRIMUS_libGLa") ||
					getenv("PRIMUS_libGL") ||
					getenv("PRIMUS_LOAD_GLOBAL") ||
					getenv("BUMBLEBEE_SOCKET")) {
				print_verbose("Optirun/primusrun detected. Skipping GPU detection");
				use_prime = 0;
			}
			
			
			
			if (use_prime == -1 && getenv("LD_LIBRARY_PATH") && !getenv("STEAM_RUNTIME_LIBRARY_PATH")) {
				String ld_library_path(getenv("LD_LIBRARY_PATH"));
				Vector<String> libraries = ld_library_path.split(":");
				for (int i = 0; i < libraries.size(); ++i) {
					if (FileAccess::exists(libraries[i] + "/libGL.so.1") ||
							FileAccess::exists(libraries[i] + "/libGL.so")) {
						print_verbose("Custom libGL override detected. Skipping GPU detection");