Add text indicating no assignees

app/main.py

@@ -102,7 +102,7 @@ def home(completed=False):
 
         for assignee in assignees:
             task.assignees += assignee.username + ", "
-        task.assignees = task.assignees[:-2]
+        task.assignees = task.assignees[:-2] if task.assignees else "[NONE]"
 
     users = db.session.execute(db.select(User)).scalars().all()