changes to group -> load_and_tag logic not returning df after processing, leading to NoneType error in summarize function.

Author: miloswrath

code/group/group.py

@@ -973,3 +973,4 @@ def summarize_task(
     def load_and_tag(self, task_code, columns, filter_col=None):
         df = self.load_task_session_data(task_code, columns)
         df = self.add_study_and_site_columns(df)
+        return df