filter by entries with no predicted release date

[xdeiimoss]

Describe your suggested feature

some entries end up with no predicted release date, so it never updates. please add a filter to know which ones are like this so we can add custom predictions to those entries.
another good approach that I would really appreciate is that for the non-predictable ones, is that we could instead choose a default frequency for all entries that doesn't have a predicted release date (even if it's completed (depending on the smart updates configuration))
the reason for the completed ones is that sometimes, the site will be marked as completed even though it isn't, which messes up smart updates.

Other details

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