NO..its definitely not safe to sleep/nap with your lenses on
Sleeping with the lenses on increases your chances of eye infection.
Your eye harbours bacteria. However the tears in your eye and the available oxygen keeps your eye healthy, thus preventing the eye from getting infected.
During waking hours you are constantly blinking. This helps in keeping the eye moist and also allows the oxygen to flow in through the tears. Lenses fit snugly over the cornea. This decreases the moisture in the eye and this in turn decreases the amount of oxygen in the eye. This decreases even further when you are asleep thus making your susceptible to the infections.