[fix] cover BC cases

lib/associations/has-many.js

@@ -45,7 +45,7 @@ module.exports = (function() {
      * Map joinTableModel/Name to through for BC
      */
     if (this.through === undefined) {
-      this.through = this.options.joinTableModel || this.options.joinTableName;
+      this.through = this.options.through = this.options.joinTableModel || this.options.joinTableName;
 
       /*
        * If both are undefined, see if useJunctionTable was false (for self associations) - else assume through to be true
@@ -105,7 +105,7 @@ module.exports = (function() {
             paired = accessor === self.associationAccessor;
           }
           // If through is not default, determine pairing by through value (model/string)
-          else {
+          else if (association.options.through) {
             paired = (self.options.through === association.options.through) ||
                      (self.options.through === association.options.through.model) ||
                      (self.options.through.model && association.options.through.model && (self.options.through.model === association.options.through.model)) ||