Oh, you can totally brick your save if you accidentally put a negative value, not even re-booting, force-closed or something along those can save you. The only way to fix it is through memory injection. Claiming more inkwells? Do you mean buying those crystal packs from the Diary Shop?
I can understand if it's a GG-done-wrong, unresolved bug from JC's part, forcing close the game midload... but you claim to haven't done those afaik, of course. Hopefully new update fixes your save. Though, we don't know when those updates are up.