Error when RelayState not provided

[explunit]

If you do not provide a RelayState querystring parameter, the following error is thrown:

     TypeError: Cannot read property 'RelayState' of undefined
      at C:\gh\node-samlp\lib\samlp.js:208:80
      at C:\gh\node-samlp\lib\samlp.js:100:5
      at Object.exports.create (C:\gh\node-samlp\node_modules\saml\lib\saml20.js:138:14)
      at getSamlResponse (C:\gh\node-samlp\lib\samlp.js:44:10)
      at execute (C:\gh\node-samlp\lib\samlp.js:200:5)
      at C:\gh\node-samlp\lib\samlp.js:228:9
      at Object.getPostURL (C:\gh\node-samlp\test\fixture\server.js:48:5)
      at C:\gh\node-samlp\lib\samlp.js:224:15
      at C:\gh\node-samlp\lib\samlp.js:26:7
      at InflateRaw.onEnd (zlib.js:166:5)
      at InflateRaw.EventEmitter.emit (events.js:117:20)
      at _stream_readable.js:920:16
      at process._tickCallback (node.js:415:13)

RelayState is optional in the SAML protocol, so this situation should not throw an error.