title: In AutoMapper 8.0 missing ResolveUsing
body: <p>Prior to AutoMapper 8.0, I have used this code:</p>
  
  <pre><code>CreateMap&lt;ApplicationRole, RoleViewModel&gt;()
  .ForMember(d =&gt; d.Permissions, map =&gt; map.MapFrom(s =&gt; s.Claims))
  .ForMember(d =&gt; d.UsersCount, map =&gt; map.ResolveUsing(s =&gt; s.Users?.Count ?? 0))
                      .ReverseMap();
  </code></pre>
  
  <p>The documentation says that you have to change ResolveUsing for MapFrom, but I have a Error "No propagation Null"</p>
  
  <pre><code>.ForMember(d =&gt; d.UsersCount, map =&gt; map.MapFrom(s =&gt; s.Users?.Count ?? 0))
  </code></pre>
  
  <p>How I have to resolve it?</p>