How to fix attempt to concatenate a nil value (field 'lastname')


ESX.RegisterServerCallback('Coolthank_board:server:getdata', function(source, cb)
    local iden = GetPlayerIdentifiers(source)[1]
    MySQL.Async.fetchAll('SELECT * FROM users WHERE identifier = @identifier LIMIT 0,1', {
        ['@identifier'] = iden
    }, function(result)
        if not (result[1] == nil) then
            local data = {}   
            local totol = {}
            local job_label = GetJobLabel(result[1].job, result[1].job_grade)     
            
     
            data =  {
                my_phonenmumber = result[1].phone_number,
                my_fullname = result[1].firstname .. " " .. result[1].lastname,

                my_job = ESX.GetPlayerFromId(source).job.label.."",
                my_ping = GetPlayerPing(source),
                players = PlayerOnline, 
                MedicConnected = MedicConnected,
                Tekno = Tekno,
                Teknik = Teknik,
                Saraphat = Saraphat,
                Archeewa = Archeewa,
                PlayerOnline = PlayerOnline,
                Mechanic = Mechanic             
               
            }

           
            cb(data)
        else
            cb(nil)
        end
    end)
end)