Serde serialization and deserialization on `Option<Option<T>`

[taitruong]

Wen serializing Some(None) and deserializing it turns to None!

launchpad/packages/sg721/src/lib.rs

Lines 89 to 91 in 111b025

	pub external_link: Option<Option<String>>,
	pub explicit_content: Option<bool>,
	pub royalty_info: Option<Option<T>>,