Update app.py

app.py

@@ -1109,6 +1109,10 @@ def getUrlBioAndAllOtherBioConcepts(word, args, key_virtuoso, cache_map_virtuoso
                         )
                         ]
 
+                    if df_expanded.empty:
+                        # nothing found from Bioportal
+                        return None, None, None, None, None, cache_map_virtuoso
+
                     # Specify the columns you want to keep
                     columns_to_keep = ["score", "from", "to", "prefLabel", "text", "@id"]