Code: sudo touch /usr/share/rtcom-messaging-ui/html/MessagingWidgetsSMSConversation.css.bkp and repeat the deinstall process. I have to 'touch' missing files all the friggin' time if something is wrong during FAPman / dpkg runs. General rule" if something's missing during executing install / deinstall scripts, touch it. The command's purpose is actually different, but the nice thing and second-usage purpose is: if a file touched doesn't exists, it is created. btw misterc: nice of you being calm with that Indian guy. I wouldn't help, because it will take AGES while repeating the same and same over again - like while calling to certain call centers...
sudo touch /usr/share/rtcom-messaging-ui/html/MessagingWidgetsSMSConversation.css.bkp