make it possible to set 0 value in layout property.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@26985 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/WebSection.py

@@ -129,7 +129,7 @@ class WebSection(Domain, PermanentURLMixIn):
       section = aq_inner(self)
       while section.getPortalType() in ('Web Section', 'Web Site'):
         result = section.getProperty(key, MARKER)
-        if result is not MARKER and result:
+        if result not in (MARKER, None):
           return result
         section = section.aq_parent
       return default