check that options.where exists before checking for key in it

lib/model.js

@@ -774,7 +774,7 @@ module.exports = (function() {
       options.attributes = Object.keys(this.rawAttributes);
     }
 
-    if (options.limit === undefined && !options.where[this.primaryKeyAttribute]) {
+    if (options.limit === undefined && !(options.where && options.where[this.primaryKeyAttribute])) {
       options.limit = 1;
     }