association.through not always defined

lib/dialects/abstract/query-generator.js

@@ -556,7 +556,7 @@ module.exports = (function() {
           }
 
           // check if model provided is through table
-          if (!as && parentAssociation && parentAssociation.through.model === model) {
+          if (!as && parentAssociation && parentAssociation.through && parentAssociation.through.model === model) {
             association = {as: Utils.singularize(model.tableName, model.options.language)};
           } else {
             // find applicable association for linking parent to this model