format can not being _MARKER for the next statements.

override its value with None


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@37819 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/mixin/downloadable.py

@@ -75,6 +75,8 @@ class DownloadableMixin:
       # By default allways return view action.
       # for all WevDAV access return raw content.
       return self.view()
+    if format is _MARKER:
+      format = None
     self._checkConversionFormatPermission(format, **kw)
     mime, data = self.convert(format, **kw)
     if not format: