It's saying that somewhere on the code there was a free() call but whatever it
tried to free was not yet allocated w/ malloc().

It also printed the memory address so any pro-mega-ultra-expert on FDRPG code
can locate which memory address (variable) you tried to free.

Please make also sure that the backup/latest was not from an old commit of
FDRPG! In this case it's very possible to happen: Although I would expect worse,
I admit.

BTW, can you reproduce the bug at any time? Can you save the game again? Can you
load the latest saved game after you save the game again? etc etc etc...