fixed hasFile

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@12923 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/Document.py

@@ -531,7 +531,8 @@ class Document(XMLObject):
     """
     _marker = []
     if getattr(self,'data', _marker) is not _marker: # XXX-JPS - use propertysheet accessors
-      return getattr(self, 'data') is not None
+      d = getattr(self, 'data')
+      return d is not None and d != ''
     return False
 
   ### Version and language getters - might be moved one day to a mixin class in base