Fix: NPE when Espionage Screen is used to move a spy and the Civs don't know each other

[SomeTroglodyte]

Regression from #14749
Fixes #14782

Raises the question - should we not suppress listing cities that the player has no knowledge of?

Edit: Raises another question - Tech Satellites should prevent the bug from triggering in the specific circumstances the issue names - starting in the future era. Sounds like a bug that triggers won't trigger properly when the gamestarter adds the techs.

Edit: Not kicking off a patch, despite the cause being deterministic - I'm estimating the conditions to be rare enough. I may be wrong.

[yairm210]

Agree that if techs aren't triggering properly when starting from era there is another bug, but this one seems pretty straightforward

[SomeTroglodyte]

Agree that if techs aren't triggering properly when starting from era there is another bug, but this one seems pretty straightforward

Exactly.

FYI, I've also checked whether a fun DiplomacyManager?.hasFlag(flag: DiplomacyFlags) = this?.hasFlag(flag) == true extension would make sense, so one could always call hasFlag directly on the result of getDiplomacyManager and get a valid answer, but I checked about half of the 32 occurrences of !!.hasFlag and found no place where the !! wasn't covered in some way, or where using that extension would significantly reduce code or improve readability = not worth it.