Old savegames may not load

[boris768]

If savegame from original game was edited in X-Com Hack, it can cause OpenXcom crash on loading (original game is not).
There are two saves in the archive, GAME2 - before editing, GAME3 - after editing.
xcom1.zip

Crashing here, base number for first alien is 20, but really there is one base. Original game just ignores invalid save data and dont crash. Please, add nullptr check and warning message here.
https://github.com/OpenXcom/OpenXcom/blob/master/src/Savegame/SaveConverter.cpp#L805

[MeridianOXC]

In my opinion, this is not in scope of OpenXcom.

What do you think @SupSuper ?