local function ChatMsgAddon(prefix, msg, channel, sender)
	if not knownPrefix[prefix] then
		DEFAULT_CHAT_FRAME:AddMessage("prefix: "..prefix.."\nmsg: "..msg.."\nchannel: "..channel.."\nsender: "..sender)
		knownPrefix[prefix] = true
	end
end

local frame = CreateFrame("frame")
frame:RegisterEvent("CHAT_MSG_ADDON")
DEFAULT_CHAT_FRAME:AddMessage("Prefixhunter loaded")
frame:SetScript("OnEvent", function(self, event, ...)
	if event == "CHAT_MSG_ADDON" then
		ChatMsgAddon(arg1, arg2, arg3, arg4)
	end
end)



 line 364:
   attempt to concatenate local 'sender' (a nil value)


364:
   attempt to concatenate local 'prefix' (a nil value)