Update evaluator.py

lm_eval/evaluator.py

@@ -625,6 +625,7 @@ def evaluate(
                 groups_agg[group]["alias"] = tab_string + group
 
         for group_name, task_list in task_hierarchy.items():
+            if task_list != []:
                 num_fewshot[group_name] = num_fewshot[task_list[0]]
 
         results_dict = {