Crash on sync when app edit before creating

[sebastienbarbier]

In some cases, front end send an edit request to a transaction which has not been created yet. Unsynced transaction have a uuid as id, where sync transaction have a PrimaryKey value as id. For some reason, the app lose track and send edit of unsynced transactions which crash backend (500), and block front-end in a cannot sync state anymore.

This ticket is about improving front end to handle better this case (avoid blocked state) and remove/fix that unexpected behaviour.