Exception at generating dossier cover

Exception on opengever.sg.

URL: http://localhost:10101/stasg/ordnungssystem/ressourcen/personal/rekrutierung/dossier-3/dossier_cover_pdf

Traceback (innermost last):

Module ZPublisher.Publish, line 60, in publish
Module ZPublisher.mapply, line 77, in mapply
Module ZPublisher.Publish, line 46, in call_object
Module grokcore.view.components, line 101, in __call__
Module zope.publisher.publish, line 107, in mapply
__traceback_info__: <bound method DossierCoverPDFView.render of <opengever.latex.dossiercover.DossierCoverPDFView object at 0x7fc7f17c2d10>>
Module zope.publisher.publish, line 113, in debug_call
Module opengever.latex.dossiercover, line 31, in render
Module ftw.pdfgenerator.browser.views, line 20, in __call__
Module ftw.pdfgenerator.browser.views, line 45, in export
Module ftw.pdfgenerator.assembler, line 25, in build_pdf
Module ftw.pdfgenerator.assembler, line 75, in render_latex
Module ftw.pdfgenerator.layout.baselayout, line 234, in render_latex_for
Module ftw.pdfgenerator.view, line 60, in render
Module opengever.latex.dossiercover, line 45, in get_render_arguments
Module ftw.pdfgenerator.view, line 72, in convert_plain
Module ftw.pdfgenerator.html2latex.converter, line 134, in convert_plain
Module ftw.pdfgenerator.utils, line 69, in encode_htmlentities
AttributeError: 'NoneType' object has no attribute 'decode'