Function null_as_default

pub fn null_as_default<'de, T, D>(deserializer: D) -> Result<T, D::Error>
where
    T: Deserialize<'de> + Default,
    D: Deserializer<'de>,

For use with serde’s deserialize_with on a sequence that must be deserialized as a single but optional (i.e. possibly null) value.