### 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 (window_mouseover_id != INVALID_WINDOW_ID && windows.has(window_mouseover_id)) {
						
						_send_window_event(windows[window_mouseover_id], WINDOW_EVENT_MOUSE_EXIT);
					}
					_send_window_event(windows[window_id], WINDOW_EVENT_MOUSE_ENTER);
				}
				CursorShape c = cursor_shape;
				cursor_shape = CURSOR_MAX;
				cursor_set_shape(c);
				window_mouseover_id = window_id;
				
				track_mouse_leave_event(hWnd);
			}
			
			if (!windows[window_id].window_has_focus && mouse_mode == MOUSE_MODE_CAPTURED) {
				break;
			}
			Ref<InputEventMouseMotion> mm;
			mm.instantiate();
			mm->set_window_id(window_id);
			if (pen_info.penMask & PEN_MASK_PRESSURE) {
				mm->set_pressure((float)pen_info.pressure / 1024);
			} else {
				mm->set_pressure((HIWORD(wParam) & POINTER_MESSAGE_FLAG_FIRSTBUTTON) ? 1.0f : 0.0f);
			}
			if ((pen_info.penMask & PEN_MASK_TILT_X) && (pen_info.penMask & PEN_MASK_TILT_Y)) {
				mm->set_tilt(Vector2((float)pen_info.tiltX / 90, (float)pen_info.tiltY / 90));
			}
			mm->set_pen_inverted(pen_info.penFlags & (PEN_FLAG_INVERTED | PEN_FLAG_ERASER));
			mm->set_ctrl_pressed(GetKeyState(VK_CONTROL) < 0);