avoiding null dbpedia problem

app.py

@@ -140,10 +140,13 @@ def query(sentence: str, state: str, years: List[str]) -> List[str]:
 
     doc = response.json()
     article = doc['bboxes'][int(doc['article_id'])]
-    
+    if len(article['lccn']['dpedia_ids']) == 0:
+        location = 'Unknown'
+    else:
+        location = article['lccn']['dpedia_ids'][0].replace('%2C_', ', ')
     results = {
         'newspaper_name': doc['lccn']['title'],
-        'location': doc['lccn']['dbpedia_ids'][0].replace('%2C_', ', '),
+        'location': location,
         'date': doc['scan']['date'],
         'article_text': article['raw_text'],
         'pdf_link': doc['scan']['jp2_url'].replace('jp2', 'pdf')