Fix checking issue

lib/jsonpath.js

@@ -39,14 +39,14 @@ function JSONPath (opts, obj, expr) {
     }
 
     opts = opts || {};
-    var len1 = arguments.length === 1;
+    var objArgs = opts.hasOwnProperty('json') && opts.hasOwnProperty('path');
     this.resultType = (opts.resultType && opts.resultType.toLowerCase()) || 'value';
     this.flatten = opts.flatten || false;
     this.wrap = opts.hasOwnProperty('wrap') ? opts.wrap : true;
     this.sandbox = opts.sandbox || {};
 
     if (opts.autostart !== false) {
-        return this.evaluate((len1 ? opts.json : obj), (len1 ? opts.path : expr));
+        return this.evaluate((objArgs ? opts.json : obj), (objArgs ? opts.path : expr));
     }
 }