Drain the tank, no flammable liquids in the dwelling, done and done. No different than a bicycle. I have been in my apt for 19 yrs now, og owners never even asked we have the same caveat in our lease now, they think the tanks are empty, and most are, no issue, what they do not know will not hurt you. Keep your rent up and don't be a pain tenant, you will be left be. A moped is your property, just like a dresser, you don't keep a gas can in your dresser do you? Drain the tank. They can't say shit.