Update app.py

app.py

@@ -57,6 +57,10 @@ df_main = df_orig.select(
     "paper_id",
 )
 
+df_main = df_main.with_columns(
+    [pl.col(col).fill_null(0).cast(pl.Int64).alias(col) for col in ["upvotes", "num_comments"]]
+)
+
 df_main = df_main.rename(
     {
         "title": "Title",