### 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)

} break;
		case WM_IME_NOTIFY: {
			return 0;
		} break;
		case WM_TOUCH: {
			BOOL bHandled = FALSE;
			UINT cInputs = LOWORD(wParam);
			PTOUCHINPUT pInputs = memnew_arr(TOUCHINPUT, cInputs);
			if (pInputs) {
				if (GetTouchInputInfo((HTOUCHINPUT)lParam, cInputs, pInputs, sizeof(TOUCHINPUT))) {
					for (UINT i = 0; i < cInputs; i++) {
						TOUCHINPUT ti = pInputs[i];
						POINT touch_pos = {
							TOUCH_COORD_TO_PIXEL(ti.x),
							TOUCH_COORD_TO_PIXEL(ti.y),
						};
						ScreenToClient(hWnd, &touch_pos);
						
						if (ti.dwFlags & TOUCHEVENTF_MOVE) {
							_drag_event(window_id, touch_pos.x, touch_pos.y, ti.dwID);
						} else if (ti.dwFlags & (TOUCHEVENTF_UP | TOUCHEVENTF_DOWN)) {
							_touch_event(window_id, ti.dwFlags & TOUCHEVENTF_DOWN, touch_pos.x, touch_pos.y, ti.dwID);
						}
					}
					bHandled = TRUE;
				} else {
					
				}
				memdelete_arr(pInputs);
			} else {