### 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)

_THREAD_SAFE_METHOD_
	p_screen = _get_screen_index(p_screen);
	ERR_FAIL_INDEX_V(p_screen, get_screen_count(), SCREEN_REFRESH_RATE_FALLBACK);
	
	if (xrandr_ext_ok) {
		XRRScreenResources *screen_info = XRRGetScreenResources(x11_display, windows[MAIN_WINDOW_ID].x11_window);
		if (screen_info) {
			RRMode current_mode = 0;
			xrr_monitor_info *monitors = nullptr;
			if (xrr_get_monitors) {
				int count = 0;
				monitors = xrr_get_monitors(x11_display, windows[MAIN_WINDOW_ID].x11_window, true, &count);
				ERR_FAIL_INDEX_V(p_screen, count, SCREEN_REFRESH_RATE_FALLBACK);
			} else {
				ERR_PRINT("An error occurred while trying to get the screen refresh rate.");
				return SCREEN_REFRESH_RATE_FALLBACK;
			}
			bool found_active_mode = false;
			for (int crtc = 0; crtc < screen_info->ncrtc; crtc++) { 
				XRRCrtcInfo *monitor_info = XRRGetCrtcInfo(x11_display, screen_info, screen_info->crtcs[crtc]);