Fix comparison with NoneType logical error

Signed-off-by: Ulincsys <[email protected]>

augur/tasks/github/pull_requests/tasks.py

@@ -231,9 +231,13 @@ def collect_pull_request_review_comments(repo_git: str, full_collection: bool) -
     repo_id = get_repo_by_repo_git(repo_git).repo_id
 
     if not full_collection:
-        # subtract 2 days to ensure all data is collected 
-        core_data_last_collected = (get_core_data_last_collected(repo_id) - timedelta(days=2)).replace(tzinfo=timezone.utc)
-        review_msg_url += f"?since={core_data_last_collected.isoformat()}"        
+        last_collected_date = get_core_data_last_collected(repo_id)
+
+        # the full_collection parameter is hardcoded to False, so we must check if there actually is a last_collected date
+        if last_collected_date:
+            # subtract 2 days to ensure all data is collected 
+            core_data_last_collected = (last_collected_date - timedelta(days=2)).replace(tzinfo=timezone.utc)
+            review_msg_url += f"?since={core_data_last_collected.isoformat()}"        
 
     pr_reviews = get_pull_request_reviews_by_repo_id(repo_id)