Check type before lowering string in list response.

test_of_time_accuracy.py

@@ -249,7 +249,7 @@ class TestOfTimeAccuracy(evaluate.Metric):
         if data:
             first_key = next(iter(data.keys()))
             if first_key in ["ordered_list", "unordered_list"] and isinstance(data[first_key], list):
-                data[first_key] = [item.lower() for item in data[first_key]]
+                data[first_key] = [item.lower() for item in data[first_key] if isinstance(item, str)]
 
         return data