The installer's ROM checker does not handle LoROMs correctly when trying to read their headers.

[Dylan Morrison]

A very minor bug given FF3 is not a LoROM, but it will probably end up spitting nonsense (or crashing) if you feed the installer a LoROM. Need to fix the routines in ROM.py for this, as I had to remove its LoROM checking code due to it not working in Python 3.

[Dylan Morrison]

Fixed in commit d416288 and then further fixed in commit b842507. LoROM/HiROM checking is now done by checking if the checksum and inverse checksum sum to 0xFFFF. If they do on the first pass, it's a LoROM, if they do on the second pass, it's a HiROM, if they don't on the second pass, it's an invalid ROM.