When /usr/bin/univention-admin-diary-entry-create in invoked without giving any command line argument, it simply prints a UUID and generated an entry in the backend named "null". Clicking on that entry does NOT open any detail page. The command probably should do nothing if no message is provided. Make option "message" required? (please read the "Note" from <https://docs.python.org/2/library/argparse.html#required>)
This issue has been filed against UCS 4.4. UCS 4.4 is out of general maintenance and components may have vastly changed in later releases. Thus, this issue is now being closed. If this issue still occurs in newer versions, please use "Clone this bug" or reopen this issue. In this case please provide detailed information on how this issue is affecting you.