Cleanup.

Author: Tratcher

src/Microsoft.AspNet.Http/Authentication/DefaultAuthenticationManager.cs

@@ -92,7 +92,7 @@ public override void Challenge(AuthenticationProperties properties, string authe
             HttpResponseFeature.StatusCode = 401;
             var handler = HttpAuthenticationFeature.Handler;
 
-            var challengeContext = new ChallengeContext(authenticationScheme, properties == null ? null : properties.Items);
+            var challengeContext = new ChallengeContext(authenticationScheme, properties?.Items);
             if (handler != null)
             {
                 handler.Challenge(challengeContext);