### 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 (strut_partial_prop != None) {
								if (XGetWindowProperty(x11_display, windows_data[win_index], strut_partial_prop, 0, LONG_MAX, False, XA_CARDINAL, &type, &format, &strut_len, &remaining, &strut_data) == Success) {
									strut_found = true;
								}
							}
							
							if (!g_bad_window && !strut_found) {
								Atom strut_prop = XInternAtom(x11_display, "_NET_WM_STRUT", True);
								if (strut_prop != None) {
									if (XGetWindowProperty(x11_display, windows_data[win_index], strut_prop, 0, LONG_MAX, False, XA_CARDINAL, &type, &format, &strut_len, &remaining, &strut_data) == Success) {
										strut_found = true;
									}
								}
							}
							if (!g_bad_window && strut_found && (format == 32) && (strut_len >= 4) && strut_data) {
								long *struts = (long *)strut_data;
								long left = struts[0];
								long right = struts[1];
								long top = struts[2];
								long bottom = struts[3];
								long left_start_y, left_end_y, right_start_y, right_end_y;
								long top_start_x, top_end_x, bottom_start_x, bottom_end_x;
								if (strut_len >= 12) {
									left_start_y = struts[4];
									left_end_y = struts[5];
									right_start_y = struts[6];
									right_end_y = struts[7];
									top_start_x = struts[8];
									top_end_x = struts[9];
									bottom_start_x = struts[10];