Revert "[epub, mobi] Fix for a problem with epubs, mobi in drama ebooks without acts"

This reverts commit 0081ccb8e51026b5af824b3c641648d23155f1e1.
Revert "Revert "[epub, mobi] Fix for a problem with epubs, mobi in drama ebooks without acts""

This reverts commit afc2b870c1646c8d6c1b754d4ee44aa059e834c9.