I'd already fixed the rule with the problem where it's been showing that now for a month or two with nothing selected.
I'm just asking if there was a better way to fix it than what I did. I expected others to have seen it before, since things like that are rarely single occurances for end users..
I haven't seen any similar reports, and my attempts of guessing at how to reproduce were not successful (including things that I might consider unusual cases that might trip it up, like disabling an action and then deleting it). If you can figure out a particular sequence of steps that reproduces the problem, that's probably what it would take to figure this out.
Assuming the rule was still working correctly, I wouldn't worry about this; if it's not, the log entries generated by the rule with (at least) Action logging enabled would be of particular interest. If you do want to "clear" it, what you did is probably the only way, unless you maybe tried other tricks like disabling and re-enabling some other action just to see if that changed anything.