Hidden toctree cause validation problems with EPUB
When you hide toctree entries somewhere in your project (not in index.rst) you get an validation error from epubcheck due to an empty ul-enviroment.
ERROR: _build/epub/Sphinx.epub/index.html(79,6): element "ul" incomplete; missing required element "li"
The hidden toctree entry is in the file with the headline "Einsatzgebiete".
Attached is the file index.html