Did you notice something in the camera after leaving the shutter cocked overnight? If not, there's no damage done. If so, what was it?
To me, the only major risk is probably battery drain. In any event, nothing will happen if you did it overnight. You could even leave the shutter cocked for weeks on end before really damaging it. I've left my M3 that way for weeks, and I think my M4-2 has also had this "experience" and they still perform well.
Now, the few times I left the shutter cocked in my M6TTL bodies I lost the batteries.
Now, I don't own a CLE, so my opinion may not be backed by experience, but from owning a few metered Leica bodies, I can tell that the only "risk" here is battery drain.
Let's see if CLE owners have something different to say. Have a fun day! 🙂