Don't allow nil dates in broken Atom feeds (#175).
Don't allow nil dates in broken Atom feeds (#175).

The case causing this issue is actually an Atom 0.3 feed, which isn't a
valid 1.0 feed.

emacsmirror/elfeed,holomorph/elfeed,skeeto/elfeed,seblemaguer/elfeed,emacsmirror/elfeed,skeeto/elfeed,holomorph/elfeed,seblemaguer/elfeed