Update index.js
Update index.js

fix the 
TypeError: Cannot convert undefined or null to object
    at DirectoryReader.<anonymous> (~/.nvm/versions/node/v6.10.2/lib/node_modules/npm-license-crawler/lib/index.js:23:85)
    at emitThree (events.js:116:13)
    at DirectoryReader.emit (events.js:194:7)
    at ~/.nvm/versions/node/v6.10.2/lib/node_modules/npm-license-crawler/lib/directoryreader.js:145:26
    at FSReqWrap.oncomplete (fs.js:123:15)
mwittig/npm-license-crawler