Empty data does not mean that cache value was not retrieved

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@29024 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/Document.py

@@ -219,8 +219,7 @@ class ConversionCacheMixin:
         md5sum, mime, data = data_list
         if md5sum != self.getContentMd5():
           raise KeyError, 'Conversion cache key is compromised for %r' % cache_id
-        if data:
-          return mime, data
+        return mime, data
     raise KeyError, 'Conversion cache key does not exists for %r' % cache_id
 
   security.declareProtected(Permissions.View, 'getConversionSize')