XEP-0050: Undefined state in § 3.4

[Flowdalic]

As reported by goffi on the standards Mailing List:

There is a little issue with XEP-0050: in section 3.4 bullet 3, it's is
said that when the element is present:

• The action "execute" is always allowed, and is equivalent to the
  action "next".
• The "next" action is typically the "next" button or option in a
  wizard. If is not contained by the , it is disabled.

So if "next" action is disabled, execute is allowed but equivalent to a
disabled action.

I have had an issue which seems related to this confusion with SleekXMPP
and Gajim: if the next action is disabled in sleekXMPP, Gajim still show
the "execute" button, but a click on it result in an error, while the
"finish" button act as expected.

My guess is that "execute" should be equivalent to "complete" when