Update app.py

app.py

@@ -21,7 +21,7 @@ def make_default_md():
     return leaderboard_md
 
 def make_arena_leaderboard_md(model_table_df):
-    total_models = len(arena_df)
+    total_models = len(model_table_df)
     leaderboard_md = f"""
 Validation Benchmark Performance is averaged.
 Final performance will be assessed at the end of the competition on a hidden test set, which may or may not be correlated with Validation performance.