Manifest will be a part of the state.Contract which will be checked on its
way to the storage. Tiny optimisation which allows not to serialize manifest
twice. Ref. https://github.com/nspcc-dev/neo-go/pull/3218#discussion_r1402374232.
Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>
Some commands don't accept arguments, but users try giving them and don't
notice a mistake. It's a bit more user-friendly to tell the user that there is
something wrong with the way he tries to use the command.
