epub converter: fix footnotes

src/epub_postprocessor.py

@@ -306,7 +306,7 @@ class EpubPostprocessor:
                                         f' While processing {internal_link_tag}')
 
                     anchor_tag = anchor_tags[0]
-                    assert anchor_tag.attrs['id'] == new_id
+                    assert anchor_tag.attrs['id'] in [new_id, a_tag_id]
                     # if anchor is found we could add placeholder for link creation on server side.
                     internal_link_tag.attrs['placeholder'] = '{{tempStyleToAnchor-' + new_id + '}}'
                     # create span to have cyclic links, link has 1 type of class, anchor another

src/html_epub_preprocessor.py

@@ -242,7 +242,8 @@ def preprocess_footnotes(source_html_tag: Tag, href2soup_html: dict = None, note
         content = footnote_tag.text
         # footnote_tag.decompose()
         footnotes.append(content)
-        new_footnotes_tags.append(footnote_tag.find(attrs={'role': 'doc-backlink'}))
+        footnote_tag = footnote_tag.find(attrs={'role': 'doc-backlink'}) or footnote_tag
+        new_footnotes_tags.append(footnote_tag)
 
     return footnotes, new_noterefs_tags, new_footnotes_tags