It's not clear from your question, whether they simply don't regard other papers in the field, or they do have related work etc. but they omit the in-body-citations.
If it is the first case, I'd second Dave's answer (unless it's a brand new question with a brand new technique that solves it, and they clearly say that no related work can be found to the best of their knowledge).
However, if it is the second case, it seems quite technical issue that can be easily fixed, and in this case you can just mention in your review that references are missing and this should be fixed (also note this to the PC chair; s/he can condition the acceptance on fixing this issue)
The fact that it's a conference, in my eyes, makes it more flexible -- papers should be considered mainly by merit and not by technicalities. I can think of the opposite case, where the paper has all the citation, gets accepted, but in the camera-ready version all references are removed.