Fix review snapshots without handwriting images

copienator/review_snapshot.py

@@ -45,8 +45,11 @@ def stage(output, staging, data, notes, *, engine, bnote=None, selected=None, fo
         merged_notes.pop(label, None)
         note = notes.get(label)
         if note is not None:
-            filename = '.review-note-' + sha256(label.encode()).hexdigest() + '.png'
-            note['img'].save(staging / filename)
+            # Grouped scans retain layout metadata even without handwriting.
+            filename = None
+            if note['img'] is not None:
+                filename = '.review-note-' + sha256(label.encode()).hexdigest() + '.png'
+                note['img'].save(staging / filename)
             merged_notes[label] = {k: v for k, v in note.items() if k != 'img'} | {'file': filename}
     payload = {'version': 1, 'engine': engine, 'data': merged_data, 'notes': merged_notes, 'bnote': bnote, 'force_filtered': sorted(retained)}
     # Roundtrip normalizes tuples while rejecting unsupported rendering data.
@@ -64,6 +67,9 @@ def load(root, output):
     notes = {}
     for label, metadata in saved['notes'].items():
         filename = metadata['file']
+        if filename is None:
+            notes[label] = {k: v for k, v in metadata.items() if k != 'file'} | {'img': None}
+            continue
         if Path(filename).name != filename:
             raise ValueError('Image manuscrite invalide.')
         with Image.open(output / filename) as image: