Exception when scaling image

[rodfersou]

At one customer server we are getting many exceptions when try to scale image data, and image data is None

AttributeError: 'NoneType' object has no attribute 'getSize'
  File "ZPublisher/Publish.py", line 138, in publish
    request, bind=1)
  File "ZPublisher/mapply.py", line 77, in mapply
    if debug is not None: return debug(object,args,context)
  File "ZPublisher/Publish.py", line 48, in call_object
    result=apply(object,args) # Type s<cr> to step into published object.
  File "opt/plone/example.org/eggs/collective.cover-1.4b1-py2.7.egg/collective/cover/browser/scaling.py", line 67, in index_html
    set_headers(self.data, self.request.response)
  File "opt/plone/example.org/eggs/plone.namedfile-3.0.9-py2.7.egg/plone/namedfile/utils.py", line 55, in set_headers
    response.setHeader('Content-Length', file.getSize())