I used to build cold finger cooled Canon 450D, and the use of dessicant was mandatory. Even if you try to seal the camera, there is always a risk, particularly if you moving from a very cold dry outside environment into a warm more humid indoor environment.
With my cold finger mods on the 450Ds, it was necessary to only allow the copper cold finger to touch the back of the sensor.
Another useful idea was to try to put a clear optical glass filter in place ahead of the sensor area, and put dry gas in there when you screw it down. This should prevent condensation inside the sensor chamber.
And worst case, it's perfectly ok to clean the sensor surface, there are cleaning swabs sold this purpose.
https://www.amazon.com.au/VSGO-Clean...8PFZZM99?gQT=1