Prevent AttributeError.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@17730 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/Document.py

@@ -581,7 +581,9 @@ class Document(XMLObject, UrlMixIn, ConversionCacheMixin, SnapshotMixin):
     # make it unique first time (before getting lastversionvalue)
     di = dict.fromkeys([r.getObject() for r in lst])
     # then get latest version and make unique again
-    di = dict.fromkeys([o.getLatestVersionValue() for o in di.keys()])
+    di = dict.fromkeys([o.getLatestVersionValue()
+                        for o in di.keys()
+                        if getattr(o, 'getLatestVersionValue', None)])
     ref = self.getReference()
     return [o for o in di.keys() if o.getReference() != ref] # every object has its own reference in SearchableText