title: No provider for NgbModalStack
body: <p>For some reason, I am suddenly getting this error out of the blue, with no code changes. Any ideas what would be causing this?</p>
  
  <p>I was able to solve this with adding <code>NgbModule.forRoot()</code> to my imports,
  but now I get this error:</p>
  
  <blockquote>
    <p>Property 'forRoot' does not exist on type 'typeof NgbModule'.</p>
  </blockquote>
  
  <p>the application is running fine otherwise.</p>