### Body

Currently `start_date` is mandatory parameter.
For DAGs with `schedule=None` we can relax this requirement as no scheduling calculation needed so the `start_date` parameter isn't used.

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
"""
        Verify the DagRun by checking for removed tasks or tasks that are not in the database yet.
        It will set state to removed or add the task if required.
        :missing_indexes: A dictionary of task vs indexes that are missing.
        :param session: Sqlalchemy ORM Session
        """
        from airflow.settings import task_instance_mutation_hook
        
        
        hook_is_noop: Literal[True, False] = getattr(task_instance_mutation_hook, "is_noop", False)
        dag = self.get_dag()
        task_ids = self._check_for_removed_or_restored_tasks(
            dag, task_instance_mutation_hook, session=session
        )
        def task_filter(task: Operator) -> bool:
            return task.task_id not in task_ids and (
                self.is_backfill
                or task.start_date <= self.execution_date
                and (task.end_date is None or self.execution_date <= task.end_date)
            )
        created_counts: dict[str, int] = defaultdict(int)
        task_creator = self._get_task_creator(created_counts, task_instance_mutation_hook, hook_is_noop)
        
        tasks_to_create = (task for task in dag.task_dict.values() if task_filter(task))
        tis_to_create = self._create_tasks(tasks_to_create, task_creator, session=session)
        self._create_task_instances(self.dag_id, tis_to_create, created_counts, hook_is_noop, session=session)
    def _check_for_removed_or_restored_tasks(