Oh okay, so if I take that out I end up back at where I was, where for some reason having [guildID] in the listener command causes it to error on seeing a nil value, if I remove that it moves onto the next command that also uses [guildID]
Lua Code:
GuildBankLedger.LibHistoireListener[guildID] = LGH:CreateGuildHistoryListener(guildID, GUILD_HISTORY_BANK)
I added a debug message to tell me what that variable was at the time and it does come back with an actual ID so not sure where its going wrong.
I had been using the code from MM to try and get this to work originally, as its the only addon I knew that did it, seeing your edits tells me im on the right path at least but not sure whats going on with that variable.
I've attached the whole file that im working with at the moment.