It's certainly safe to drink! However over time, the scotch can evaporate (Angel's Share) even when capped! I do not think that just one night (less than 24 hours), there will be any significant change. I"m sure that if this has happened to someone else, they will certainly correct me
Take a drink and be the best judge here - let us know. Cheers!
PS Do not leave the cap off again - just a friendly reminder : )