Basically you reverse the @if@. So in the below one I posted, it will look for a target after the command, if no target, then it will do @user@ one, and if you put something after the command, it will do the @target@. Here you go:
!addcom !nap @if@[@target@||||@user@ have a good nap ResidentSleeper||@target@ have a good nap ResidentSleeper]