After I just updated the package, I was able to run qterminal again.
apt policy qterminal
qterminal:
Installed: 1.4.0-1
Installation candidate: 1.4.0-1
Version table:
*** 1.4.0-1 500
500 http://ftp.de.debian.org/debian unstable/main amd64 Packages
100 /var/lib/dpkg/status
...
edlin