attempt to concatenate local 'playerName' (a nil value)

[BloodDragon]

Hey, I need your help.
My addon GildenSteuer sometimes shows the error after porting from a dungeon or using a portal:

1x GildenSteuer\GildenSteuer-3.4.lua:377: attempt to concatenate local 'playerName' (a nil value)

That is the line with the error:

self:Debug("Add status request for " .. playerName .. " to queue")

Here is the Lines:

function GildenSteuer:RequestStatus(playerName, timestamp)
    self:Debug("Add status request for " .. playerName .. " to queue")
    if timestamp == nil then
        timestamp = self:GetPlayerStatusDB(playerName, true).timestamp
    end
    local data = {"S", playerName}
    if timestamp ~= nil then
        table.insert(data, timestamp)
    end
    table.insert(self.outgoingQueue, data)
end

I hope anyone can help me.