title: SpecFlow Generation error: Object not set to an instance of an object
body: <p>I am trying to build a solution with SpecFlow tests in it. These have built and run previously. I am using:</p>
  
  <ul>
  <li>Visual Studio 15.3.2</li>
  <li>VS Extension: SpecFlow for VS2017 version 2017.1.6 </li>
  <li>NuGet package: SpecFlow 2.2.0</li>
  <li>NuGet package: NUnit 3.7.1</li>
  </ul>
  
  <p>I changed one specflow definition file and now I get: #error Generation error: Object reference not set to an instance of an object.</p>
  
  <p>Any other specflow definition file now fails with the same message if touched. The only recent change to my system was an update to VS which had just come out of RC</p>