ui: avoid mutable default arguments I almost introduced a bug around this code by accidentally mutating a default argument. There's no reason for these to exist. It is OK to not assign {} to environ in ui.system because util.system knows how to deal with that.

util: avoid mutable default arguments I almost introduced a bug around this code by accidentally mutating a default argument. There's no reason for these to exist.

obsstore: fast path to check if obsstore is empty