[BUG] Reopening a roll call fails in some execution flows

[matteosz]

Description (Actual behavior)

These errors are generated from the servers.

An error response was replied by the server
Error -4 - invalid message field: failed to publish: failed to handle publish message: failed to process message: failed to process action 'roll_call#reopen': The field `opens` does not correspond to the id of the previous roll call message]
com.github.dedis.popstellar.utility.error.JsonRPCErrorException: Error -4 - invalid message field: failed to publish: failed to handle publish message: failed to process message: failed to process action 'roll_call#reopen': The field `opens` does not correspond to the id of the previous roll call message]

Expected behavior

The error shouldn't happen.

How to reproduce

It happens when the organizer creates, opens and close a Roll Call X. Then it creates a Roll Call Y (to be opened in the future), then tries to reopen the roll call X.

Version & Environment

This bug was reproduced on this commit, however it was present since this other commit.

Front-ends:

• [ ] Fe1-Web (please include browser's names & version)
• [ ] Fe2-Android (please specify if phone or emulation, and Android version)
• [X] Not applicable

Back-ends:

• [X] Be1-Go
• [X] Be2-Scala
• [ ] Not applicable

Workaround

No workaround, the roll call can't simply be reopened.