Update app.py

app.py

@@ -53,13 +53,15 @@ def insert_sentence(text, sentence, interval):
 
 def format_bibtex(paper, style='apa'):
     bibtex_entry = paper["citationStyles"]["bibtex"]
-    bib_data = parse_string(bibtex_entry, 'bibtex')
-    formatter = find_plugin('pybtex.style.formatting', style)()
-    entries = list(bib_data.entries.values())
-    if not entries:
-        return "No valid entries found."
-    formatted_entry = formatter.format_entries(entries)
-    return '\n'.join(entry.text.render_as('text') for entry in formatted_entry)
+    try:
+        bib_data  = parse_string(bibtex_entry, 'bibtex')
+        formatter = find_plugin('pybtex.style.formatting', style)()
+        entries   = list(bib_data.entries.values())
+        formatted = formatter.format_entries(entries)
+        return '\n'.join(e.text.render_as('text') for e in formatted)
+    except MissingFieldError:
+        # Fallback:  ▸ return raw BibTeX ▸ or convert to a safe @misc record
+        return bibtex_entry.strip()
 
 def search_paper(query):
     SEMANTIC_SCHOLAR_API_URL = "https://api.semanticscholar.org/graph/v1/paper/"