ChatControlBase: fix autoscroll on keyboard shortcuts
The issue reported by concerto [1] is a regression since af312830.
[1] https://conference.gajim.org:5281/muc_log/gajim/2019-09-10#df591057-8693-4e76-bbc2-334d839c6adc
The issue reported by concerto [1] is a regression since af312830.
[1] https://conference.gajim.org:5281/muc_log/gajim/2019-09-10#df591057-8693-4e76-bbc2-334d839c6adc