Admit to the absence and you will have to go to the CJ.
Don't admit to the absence and get caught and you will have to go to the CJ. Given your lack of a buffer in absences, it is quite possible you will be getting an RQ, be requested to produce border records, etc. If you withdrew your application and reapplied now, would you qualify with a bit more of a buffer? Of course, withdrawing your application means you would probably be getting an RQ on the new application, but perhaps not such a big deal if you have more of a buffer.
One effect of the new citizenship law is that CIC is going to be bombarded with applications in the next several months of people that just barely met the residency requirement. It seems likely everything is going to slow down again as CIC looks closely at such applications.