Fixed bug that didn't reset completion flags properly when clearing story mode and starting arcade without restarting the game first.

Thanks to a report by user tunegoro (catlover_mimi), I have identified a bug that didn't reset a specific flag after clearing story mode and starting arcade mode immediately after. The bug should now be fixed. You might need to restart Arcade mode, though, if you met this bug during your run, as the save file was technically corrupted by the bug in question.