Fix intermittent test failure

[programaker]

[info] PersistentGameProgress_Properties:
[info] - converting a GameProgress into PersistentGameProgress and back, gives the same GameProgress as Some
[info] - converting an invalid PersistentGameProgress to GameProgress gives None *** FAILED ***
[info]   TestFailedException was thrown during property evaluation.
[info]     Message: Some(GameProgress(MainCharacter(,Female,43,0),Vector(),0,Set())) was not empty
[info]     Location: (PersistentGameProgress_Properties.scala:83)
[info]     Occurred when passed generated values (
[info]       arg0 = PersistentMainCharacter(,Female,43,0), // 3 shrinks
[info]       arg1 = 14, // 3 shrinks
[info]       arg2 = Vector(),
[info]       arg3 = 0, // 27 shrinks
[info]       arg4 = List() // 2 shrinks
[info]     )