message: put the code that checked if undefined back
diff: @@ -158,6 +158,9 @@ class AlexaInteractionModel {
  _.set(alexaModel, 'interactionModel.languageModel.invocationName', model.invocation);
  // handle invocation name requirements
  + if (alexaModel.interactionModel.languageModel.invocationName.length === 0) {
  + throw new Error(errorPrefix + 'Invocation cannot be empty');
  + }
  if (alexaModel.interactionModel.languageModel.invocationName.length < 2 ||
  alexaModel.interactionModel.language.invocationName.length > 50) {
  throw new Error(errorPrefix + 'Invocation name must be between 2 and 50 characters.');
  