Fix empty model check; misses only complex types

Author: commonsensesoftware

src/Common/src/Common.OData/OData/VersionedODataModelBuilder.cs

@@ -110,11 +110,10 @@ private void BuildModelPerApiVersion(
                 configurations[j].Apply( builder, apiVersion, routePrefix );
             }
 
+            const int EntityContainerOnly = 1;
             var model = builder.GetEdmModel();
             var container = model.EntityContainer;
-            var empty = !container.EntitySets().Any() &&
-                        !container.Singletons().Any() &&
-                        !container.OperationImports().Any();
+            var empty = model.SchemaElements.Count() == EntityContainerOnly;
 
             if ( empty )
             {