Fix if check to account for non node people

Author: Michael Keating

astar.js

@@ -6,7 +6,7 @@
 // http://eloquentjavascript.net/appendix2.html
 
 (function(definition) {
-    if(typeof module.exports === 'object') {
+    if(typeof module === 'object' && typeof module.exports === 'object') {
         module.exports = definition();
     } else if(typeof define === 'function' && define.amd) {
         define([], definition);