Error log

Hi Jan,

Thanks for the report. This looks like a small bug with a variable initialization in the books widget and should occurs, if there is no book selected in the admin area of the widget.

This can be fixed, see: https://github.com/winkm89/teachPress/commit/6ecaed723f480c9b16acd0444c4d00d23303012e (This patch will also be a part of the next version.)