**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
else:
                    suc_count += 1
            flash("{} variable(s) successfully updated.".format(suc_count))
            if fail_count:
                flash("{} variable(s) failed to be updated.".format(fail_count), 'error')
            self.update_redirect()
            return redirect(self.get_redirect())
class JobModelView(AirflowModelView):
    """View to show records from Job table"""
    route_base = '/job'
    datamodel = AirflowModelView.CustomSQLAInterface(BaseJob)  
    base_permissions = ['can_list']
    list_columns = ['id', 'dag_id', 'state', 'job_type', 'start_date',
                    'end_date', 'latest_heartbeat',
                    'executor_class', 'hostname', 'unixname']
    search_columns = ['id', 'dag_id', 'state', 'job_type', 'start_date',
                      'end_date', 'latest_heartbeat', 'executor_class',
                      'hostname', 'unixname']
    base_order = ('start_date', 'desc')
    base_filters = [['dag_id', DagFilter, lambda: []]]
    formatters_columns = {
        'start_date': wwwutils.datetime_f('start_date'),
        'end_date': wwwutils.datetime_f('end_date'),
        'hostname': wwwutils.nobr_f('hostname'),
        'state': wwwutils.state_f,
        'latest_heartbeat': wwwutils.datetime_f('latest_heartbeat'),
    }
class DagRunModelView(AirflowModelView):
    """View to show records from DagRun table"""
    route_base = '/dagrun'