This change makes the treatment of params and meta the same, by
assigning a well-known pointer at first to detect if the unmarshaling
process overwrites it with an explicit nil, or it stays the same in
which it means that it was unset from the beginning.
This change makes the treatment of params and meta the same, by assigning a well-known pointer at first to detect if the unmarshaling process overwrites it with an explicit nil, or it stays the same in which it means that it was unset from the beginning.