### Discussed in https://github.com/apache/airflow/discussions/19366

<div type='discussions-op-text'>

<sup>Originally posted by **a-pertsev** November  2, 2021</sup>
### Apache Airflow version

2.2.1 (latest released)

### Operating System

Ubuntu 20.04 LTS

### Versions of Apache Airflow Providers

apache-airflow-providers-amazon==2.3.0
apache-airflow-providers-apache-cassandra==2.1.0
apache-airflow-providers-ftp==2.0.1
apache-airflow-providers-google==6.0.0
apache-airflow-providers-http==2.0.1
apache-airflow-providers-imap==2.0.1
apache-airflow-providers-jdbc==2.0.1
apache-airflow-providers-mysql==2.1.1
apache-airflow-providers-postgres==2.3.0
apache-airflow-providers-presto==2.0.1
apache-airflow-providers-slack==4.1.0
apache-airflow-providers-sqlite==2.0.1

### Deployment

Virtualenv installation

### Deployment details

_No response_

### What happened

Got error when manually run newly created task in already finished dag run (in UI).

### What you expected to happen

"Run" button should work without exceptions.

### How to reproduce

1. Define a dag with some tasks.
2. Create dag run (manually or by schedule)
3. Add new task into dag, deploy code
4. Select new task in UI and press "Run" button

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
</div>
airflow/www/views.py
"""Get Dag details."""
        dag_id = request.args.get('dag_id')
        dag = current_app.dag_bag.get_dag(dag_id)
        dag_model = DagModel.get_dagmodel(dag_id)
        title = "DAG Details"
        root = request.args.get('root', '')
        wwwutils.check_import_errors(dag.fileloc, session)
        states = (
            session.query(TaskInstance.state, sqla.func.count(TaskInstance.dag_id))
            .filter(TaskInstance.dag_id == dag_id)
            .group_by(TaskInstance.state)
            .all()
        )
        active_runs = models.DagRun.find(dag_id=dag_id, state=State.RUNNING, external_trigger=False)
        tags = session.query(models.DagTag).filter(models.DagTag.dag_id == dag_id).all()
        return self.render_template(
            'airflow/dag_details.html',
            dag=dag,
            title=title,
            root=root,
            states=states,
            State=State,
            active_runs=active_runs,
            tags=tags,
            dag_model=dag_model,
        )
    @expose('/rendered-templates')