handle hasOne onDelete cascade when no associate

lib/query-interface.js

@@ -651,6 +651,10 @@ QueryInterface.prototype.delete = function(instance, tableName, identifier, opti
       if (!Array.isArray(instances)) instances = [instances];
 
       return Promise.each(instances, function (instance) {
+        if (!instance) {
+          return Promise.resolve();
+        }
+
         return instance.destroy({
           transaction: options.transaction,
           logging: options.logging