Don't blow up if we have references to non-existant products laying around

lib/python/HelpSys/HelpSys.py

@@ -258,6 +258,7 @@ class ProductHelp(Acquisition.Implicit, ObjectManager, Item, Persistent):
             if hasattr(topic,'isAPIHelpTopic') and topic.isAPIHelpTopic:
                 apitopics.append(topic)
             else:
+                try:
                     if callable(topic.id):
                         id=topic.id()
                     else:
@@ -269,6 +270,10 @@ class ProductHelp(Acquisition.Implicit, ObjectManager, Item, Persistent):
                         zpttopics.append(topic)
                     else:
                         topics.append(topic)
+                except ImportError:
+                    # Don't blow up if we have references to non-existant
+                    # products laying around
+                    pass
         if dtmltopics:
             topics = topics + [TreeCollection(' DTML Reference', dtmltopics)]
         if apitopics: