### 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 ((p_new_driver == "wintab") && wintab_available) {
			wintab_WTInfo(WTI_DEFSYSCTX, 0, &wd.wtlc);
			wd.wtlc.lcOptions |= CXO_MESSAGES;
			wd.wtlc.lcPktData = PK_STATUS | PK_NORMAL_PRESSURE | PK_TANGENT_PRESSURE | PK_ORIENTATION;
			wd.wtlc.lcMoveMask = PK_STATUS | PK_NORMAL_PRESSURE | PK_TANGENT_PRESSURE;
			wd.wtlc.lcPktMode = 0;
			wd.wtlc.lcOutOrgX = 0;
			wd.wtlc.lcOutExtX = wd.wtlc.lcInExtX;
			wd.wtlc.lcOutOrgY = 0;
			wd.wtlc.lcOutExtY = -wd.wtlc.lcInExtY;
			wd.wtctx = wintab_WTOpen(wd.hWnd, &wd.wtlc, false);
			if (wd.wtctx) {
				wintab_WTEnable(wd.wtctx, true);
				AXIS pressure;
				if (wintab_WTInfo(WTI_DEVICES + wd.wtlc.lcDevice, DVC_NPRESSURE, &pressure)) {
					wd.min_pressure = int(pressure.axMin);
					wd.max_pressure = int(pressure.axMax);
				}
				AXIS orientation[3];
				if (wintab_WTInfo(WTI_DEVICES + wd.wtlc.lcDevice, DVC_ORIENTATION, &orientation)) {
					wd.tilt_supported = orientation[0].axResolution && orientation[1].axResolution;
				}
				wintab_WTEnable(wd.wtctx, true);
			} else {
				print_verbose("WinTab context creation failed.");
			}
		}
	}
}
DisplayServer::WindowID DisplayServerWindows::_create_window(WindowMode p_mode, VSyncMode p_vsync_mode, uint32_t p_flags, const Rect2i &p_rect) {