SIENTIAPDE-1110

Update MongoDB activity to handle None last_data_timestamp by using an empty filter, improving data retrieval logic.

scouter/activities/mongodb.py

@@ -92,6 +92,9 @@ class MongoDB(BaseActivity):
 
         try:
 
+            if last_data_timestamp is None:
+                data_filter = {}
+            else:
                 data_filter = {
                     "inserted_at": {
                         "$gt": datetime.strptime(last_data_timestamp, "%Y-%m-%d %H:%M:%S.%f")