Fix to default columns of a lookup, and fixed another bug in lookups

InABox.Core/ILookupDefinition.cs

@@ -135,7 +135,7 @@ namespace InABox.Core
 
         private static ILookupDefinitionGenerator? GetLookupGenerator(IProperty? property)
         {
-            var generator = property?.Parent?.GetAttribute<LookupDefinitionAttribute>()?.Generator
+            var generator = property?.GetAttribute<LookupDefinitionAttribute>()?.Generator
                 ?? (property != null ? _lookupGenerators.GetValueOrDefault(property) : null);
             return generator != null
                 ? Activator.CreateInstance(generator) as ILookupDefinitionGenerator
@@ -313,6 +313,10 @@ namespace InABox.Core
                     columns.Add(prop);
                 }
             }
+            if (!columns.Any())
+            {
+                columns.DefaultColumns();
+            }
 
             return columns;
         }