Do not errase dict if the new property is empty. Set the new property only it

there is a value related to it. This way we keep less pirioritary result in
 case the more prioritary is empty, but at least we have a result.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@37481 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/Document.py

@@ -753,7 +753,10 @@ class Document(DocumentExtensibleTraversableMixin, XMLObject, UrlMixIn, CachedCo
       else:
         result = method()
       if result is not None:
-        kw.update(result)
+      if result is not None:
+        for key, value in result.iteritems():
+          if value not in (None, ''):
+            kw[key]=value
 
     if file_name is not None:
       # filename is often undefined....