title: T4MVC failing to generate classes with ErrorGeneratingOutput
body: <p>My MVC project has used T4MVC for scaffolding working fine for years.  I made a change to the parameter inputs for one of my controller methods and for some reason when I ran "Run Custom Tool" to pick up the changes, it instead over wrote the T4MVC.cs file with the text "ErrorGeneratingOutput".</p>
  
  <p>I tried backing out the changes with no effect.  I also cleaned and tried rebuilding the project multiple times but now there is just no classes under T4MVC.tt and it still fails the same way when trying to regenerate everything.</p>
  
  <p>When I attempt to debug the template ("Debug T4 Template") it over writes T4MVC.cs file with "ErrorDebuggingTemplate" instead.</p>
  
  <p>I also tried updating T4MVC to the latest version on nuget (3.17.4) but that didn't change the behavior at all.</p>
  
  <p>Until this is fixed I can't push any changes as the project now reports thousands of errors (most missing assembly references) so would really appreciate any help getting this resolved.  Thanks.</p>