Just picked up a refurbished Lenovo T420. Been working through setting up 16.04 on it and have run into issues with Xscreensaver daemon not running at startup. Found an answer to the problem. The OP said he went to his core applications file and found 'screensaver - empty'. He added 'screensaver - xscreensaver' and that took care of the problem. I don't know which file he was referring to and my google efforts haven't turned up an answer.
I have already setup the startup applications file command 'xscreensaver -nosplash'. Tried a variation I saw posted 'xscreensaver -no-splash'. Neither corrected the issue. So, I am trying to locate the file he edited.