[Bug][SP] State of missions not saved

[JanB1]

Description: When loading a previously saved game, the state of the missions is not saved. Previously offered/visible missions are not visible any more, and previously completed missions are marked as incomplete.

Steps to reproduce:

1. Accept a mission from the Overthrow game interface
2. Complete the mission and get the reward
3. Save game and leave to main menu
4. Reload game
5. Mission is not marked as complete any more, but player still has the rewards previously gained

Severity: Potential exploit