Help documentation not reachable via webapp

[dstenger]

Describe the bug
The help documentation of a deegree OGC API webapp which is linked in HTML view at the bottom left is not reachable and displays an empty page instead.
The reference implementation can be used to reproduce the bug: http://cite.deegree.org/deegree-ogcapi-1.3/datasets/kitaeinrichtung

To Reproduce
Steps to reproduce the behavior (here example for HTML encoding):

1. Go to http://cite.deegree.org/deegree-ogcapi-1.3/datasets or http://cite.deegree.org/deegree-ogcapi-1.3/datasets/kitaeinrichtung
2. Click on "Help" at the bottom left
3. Documentation is not shown and white site is displayed instead

Expected behavior
Documentation shall be displayed.

Desktop (please complete the following information):

• Version: 1.3
• Datasource: postgres/postgis
• Browser: firefox
• GIS-Client: web browser