Index: EngineSource/ClassicBehaviors.cs
===================================================================
--- EngineSource/ClassicBehaviors.cs	(revision 641)
+++ EngineSource/ClassicBehaviors.cs	(working copy)
@@ -192,7 +192,7 @@
                             result += "\t* \"" + topic.DottedName + "\":" + topic.Namespace + ".[" + topic.LocalName + "]" + Environment.NewLine;
                         }
                         string topicSummary = ctx.CurrentFederation.GetTopicPropertyValue(topic, "Summary");
-                        if (topicSummary.Length > 0)
+                        if ((!(topicSummary == null)) && (topicSummary.Length > 0))
                         {
                             result += "\t\t*" + topicSummary + Environment.NewLine;
                         }
@@ -200,7 +200,7 @@
                     else
                     {
                         string topicProperty = ctx.CurrentFederation.GetTopicPropertyValue(topic, arg2);
-                        if (topicProperty.Length > 0)
+                        if ((!(topicProperty == null)) && (topicProperty.Length > 0))
                         {
                             result += "\t* \"" + topic.DottedName + "\":" + topic.Namespace + ".[" + topic.LocalName + "]" + Environment.NewLine + "\t\t* " + topicProperty + Environment.NewLine;
                         }