Ubutu does not Hibernate with DL driver installed
 

I have Ubuntu 18.04 DL driver 4.4.24.
No DL adpater is coonected to the system and I do sudo pm-hibernate. The hibernate command does not end, no hibernate occurs and Ubuntu is running.
The pm-suspend.log shows as last line:

"Running hook /etc/pm/sleep.d/displaylink.sh hibernate hibernate:"

My displaylink.sh looks:

#!/bin/bash
# Copyright (c) 2015 DisplayLink (UK) Ltd.

suspend_dlm()
{
#flush any bytes in pipe
while read -n 1 -t 1 SUSPEND_RESULT < /usr/lib/displaylink/PmMessagesPort_out; do : ; done;

#suspend DisplayLinkManager
echo "S" > /usr/lib/displaylink/PmMessagesPort_in

#wait until suspend of DisplayLinkManager finish
read -n 1 -t 10 SUSPEND_RESULT < /usr/lib/displaylink/PmMessagesPort_out
}

resume_dlm()
{
#resume DisplayLinkManager
echo "R" > /usr/lib/displaylink/PmMessagesPort_in
}

case "$1" in
thaw)
resume_dlm
;;
hibernate)
suspend_dlm
;;
suspend)
suspend_dlm
;;
resume)
resume_dlm
;;
esac

It seems to me that the displaylink.sh is waiting for an DL driver status change, but DL driver is not aktiv because I has it not connected.
I expect there is a missing check for DL driver active!!!!