check ptr is aligned to `UD`

[github-actions[bot]]

source

	pub fn userdata(&self) -> Option<&mut Userdata> {
		let f = self.1.get_userdata();
		let ptr = unsafe { f(self.0) };
		if ptr.is_null() {
			None
		} else {
			let ptr = ptr as *mut Userdata;
			// TODO: check ptr is aligned to `UD`
			unsafe { ptr.as_mut() }
		}
	}