@Toycept As long as you cover the jar this is an acceptable practice. The reason for the cover is to avoid condensation in the chamber. Excess condensation can find its way into the electronics enclosure and while it is not a safety risk, it is not the ideal environment for the electronics.
It is preferred to use glycerin for combating oxygen inhibition though. You can purchase vegetable glycerin by the gallon and it can be reused several times. The glycerin provides a more uniform surface (water can leave white discoloration and cause texture changes) and does not evaporate, therefore does not condensate.