Fixing an unwrap on bad patches in unrecord (these patches cannot even be produced outside of bugs)

Dependencies

• [2] KQTD46KV Unrecord: restore files *after* having unapplied the *entire* change
• [*] SXEYMYF7 Fixing the bad changes in history (unfortunately, by rebooting).

Change contents

• edit in libpijul/src/unrecord/mod.rs at line 190
  [2.200]

  [2.200]
  + Atom::EdgeMap(ref newedges) if newedges.edges.is_empty() => {}