Autotests found that after PMM installation Update widget displays Available version for update as unknown.
I reproduced this just a couple of times. So I guess the problem appears only with some network problem.
But I think in this case widget shouldn't display possibility for update , I mean 'Update to unknown'
So if available version is unknown, show only text "No updates are available"
Let's use in this case "latest" instead of 'unknow'
(This is case when Update system gives us Good response but version number can't be extracted)
Later, when we'll do Conditions for update - this will be revisited