My local LEOs almost always have their hand resting on the grip of their weapon. If it's not 'brandishing' when they're talking to me or exerting authority, it should be no different for me.
I've done it before while talking to them at the shop and they don't seem to be too appreciative. They seem to stop in my presence at least, so I stop too. ;0
But back to the point at hand, no harm, no foul, at least as far as I'm concerned.