**Apache Airflow version**:

master

**Kubernetes version (if you are using kubernetes)** (use `kubectl version`):

**Environment**: breeze

**What happened**:

This DAG
```python
from airflow import models
from airflow.operators.dummy_operator import DummyOperator
from airflow.utils.dates import days_ago

with models.DAG("test", start_date=days_ago(1), schedule_interval=None,) as dag:
    t1 = DummyOperator(task_id="t1")
    t2 = DummyOperator(task_id="t2")
    t1 >> t2
```

is rendering like that:

<img width="1374" alt="Screenshot 2020-08-27 at 19 59 41" src="https://user-images.githubusercontent.com/9528307/91478403-11d7fb00-e8a0-11ea-91d0-d7d578bcb5a2.png">

**What you expected to happen**:

I expect to see same relations as defined in DAG file

**How to reproduce it**:

Render the example DAG from above.


**Anything else we need to know**:

I'm surprised by this bug 👀 

airflow/www/views.py
@has_dag_access(can_dag_read=True)
    @has_access
    @action_logging
    @provide_session
    def redirect_to_external_log(self, session=None):
        """Redirects to external log."""
        dag_id = request.args.get('dag_id')
        task_id = request.args.get('task_id')
        execution_date = request.args.get('execution_date')
        dttm = timezone.parse(execution_date)
        try_number = request.args.get('try_number', 1)
        ti = session.query(models.TaskInstance).filter(
            models.TaskInstance.dag_id == dag_id,
            models.TaskInstance.task_id == task_id,
            models.TaskInstance.execution_date == dttm).first()
        if not ti:
            flash(f"Task [{dag_id}.{task_id}] does not exist", "error")
            return redirect(url_for('Airflow.index'))
        task_log_reader = TaskLogReader()
        if not task_log_reader.supports_external_link:
            flash("Task log handler does not support external links", "error")
            return redirect(url_for('Airflow.index'))
        handler = task_log_reader.log_handler
        url = handler.get_external_log_url(ti, try_number)
        return redirect(url)
    @expose('/task')
    @has_dag_access(can_dag_read=True)
    @has_access
    @action_logging
    def task(self):