Fix a bug with codec that cause node to panic.
Fix a bug with codec that cause node to panic.

alekseysidorov/exonum,alekseysidorov/exonum,exonum/exonum,exonum/exonum,exonum/exonum,alekseysidorov/exonum,alekseysidorov/exonum,exonum/exonum