Fixes a bug whereby NetworkManager would be updated to version "rc2".
* guix/import/gnome.scm (latest-gnome-release)[even-minor-version?]:
Change catch-all case to return #f when the first part is not a digit.
This is a followup to 81c3dc3224.
* guix/import/gnome.scm (jsonish->upstream-source): Use 'assoc-ref'
instead of 'hash-ref'.
(latest-gnome-release): Match a vector containing an alist, not a hash
table. Use 'fold' instead of 'hash-fold' over RELEASES.