The demo does not end there at all, there is a proper ending for the level, where you must rescue Jan, and fight a sabre battle before that. Search around for the keypad to open the door. If I remember correctly, is this in the large central chamber, with a pillar through the middle and many floors? If it is, the control should be inside the pillar at the top floor, where an Imperial Officer is.
Do I really need to fill this in?
Surely my radiant personality is evident from my posts.