message: Fixed null variable on OCPPService logging
diff: @@ -777,7 +777,7 @@ export default class OCPPService {
  }
  // Save
  await TransactionStorage.saveTransaction(tenant.id, lastTransaction);
  - } else if (!Utils.isUndefined(lastTransaction)) {
  + } else if (!Utils.isNullOrUndefined(lastTransaction)) {
  await Logging.logWarning({
  tenantID: tenant.id,
  source: chargingStation.id,
  