NODE_PATH env variable could be undefined

Author: anru

file-system-loader.js

@@ -69,10 +69,14 @@ var FileSystemLoader = (function () {
 
         // if the path is not relative or absolute, try to resolve it in node_modules
         if (newPath[0] !== '.' && newPath[0] !== '/') {
+          var paths;
+          if (process.env.NODE_PATH) {
+            paths = process.env.NODE_PATH.split(_path2['default'].delimiter);
+          }
           try {
             fileRelativePath = nodeResolve.sync(newPath, {
               basedir: rootRelativeDir,
-              paths: process.env.NODE_PATH.split(_path2['default'].delimiter)
+              paths: paths
             });
             // in this case we need to actualize rootRelativePath too
             rootRelativePath = _path2['default'].relative(_this.root, fileRelativePath);