title: Query works Mutations fail: Expected non-null value, resolve delegate return null
body: <p>I have a GraphQL .Net Core server and queries resolve wonderfully. Mutations however are failing with this error.</p>
  
  <blockquote>
    <p>"message": "Expected non-null value, resolve delegate return null for \"$GraphQLCore.Types.SInputType\"",</p>
  </blockquote>
  
  <p>I understand that you do not reuse your query types for mutations and I have created separate types but I'm still missing something.</p>
  
  <pre><code>public class SInputType : InputObjectGraphType
  {
      public SInputType()
      {
          Field&lt;IntGraphType&gt;("sid");
           ...etc
      }
  }
  
  public class SUpdateMutation : ObjectGraphType
  {
      MutationMock mm = new MutationMock();
  
      public SUpdateMutation()
      {
          Field&lt;SInputType&gt;(
              "createSrecord", 
              arguments: new QueryArguments(new QueryArgument&lt;SInputType&gt; 
                         { Name = "sticker"}),
              resolve: context =&gt; {
                  var _stik = context.GetArgument&lt;SModel&gt;("stick");
                  return mm.StockMutation(stick);
              });
      }
  
  }
  </code></pre>
  
  <p>Everything I come up with on Goggle is related to NOT using a InputObjectGraphType but I am and from the examples I see I am using it correctly???</p>
  
  <p>So any input or pointers would be greatly appreciated.</p>
  
  <p>TIA</p>