fix: show 'no page-image found' for skipped pages in split page view

Signed-off-by: jhchoi1182 <[email protected]>

Author: jhchoi1182

docling_core/transforms/serializer/html.py

@@ -1068,7 +1068,7 @@ def _serialize_page_img(page_img: Image):
 
                 if is_skipped_page:
                     # Render empty figure for skipped page (same structure as normal)
-                    html_parts.append("<figure></figure>")
+                    html_parts.append("<figure>no page-image found</figure>")
                 else:
                     page_img = self.doc.pages[page_no].image
                     vized_page = vized_pages_dict.get(page_no)