### 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)

}
				AXIS orientation[3];
				if (wintab_WTInfo(WTI_DEVICES + wd.wtlc.lcDevice, DVC_ORIENTATION, &orientation)) {
					wd.tilt_supported = orientation[0].axResolution && orientation[1].axResolution;
				}
			} else {
				print_verbose("WinTab context creation failed.");
			}
		} else {
			wd.wtctx = 0;
		}
		if (p_mode == WINDOW_MODE_MAXIMIZED) {
			wd.maximized = true;
			wd.minimized = false;
		}
		if (p_mode == WINDOW_MODE_MINIMIZED) {
			wd.maximized = false;
			wd.minimized = true;
		}
		wd.last_pressure = 0;
		wd.last_pressure_update = 0;
		wd.last_tilt = Vector2();
		
		wd.im_himc = ImmGetContext(wd.hWnd);
		ImmAssociateContext(wd.hWnd, (HIMC)0);
		wd.im_position = Vector2();
		if (p_mode == WINDOW_MODE_FULLSCREEN || p_mode == WINDOW_MODE_EXCLUSIVE_FULLSCREEN || p_mode == WINDOW_MODE_MAXIMIZED) {
			RECT r;
			GetClientRect(wd.hWnd, &r);
			ClientToScreen(wd.hWnd, (POINT *)&r.left);