## Bug description

Trying to look at insights for feature flags no longer works (see screenshot below).

<img width="1329" alt="" src="https://user-images.githubusercontent.com/5864173/100642031-de24cb00-32fd-11eb-88b4-047c4f82124f.png">


Removing the breakdown works but then you can't see the difference between the binary values.

![image](https://user-images.githubusercontent.com/5864173/100642046-e2e97f00-32fd-11eb-8ae5-4238f899c8b8.png)


## Expected behavior

Insights should be shown as before.


## How to reproduce

1. Click on the insights link on any feature flag row.

## Environment

Cloud (Clickhouse).

## Additional context



#### *Thank you* for your bug report – we love squashing them!

ee/clickhouse/queries/test/test_trends.py
self._create_events()
        
        with freeze_time("2020-01-04T13:01:01Z"):
            response = ClickhouseTrends().run(
                Filter(
                    data={
                        "date_from": "-14d",
                        "breakdown": "$some_property",
                        "events": [
                            {"id": "sign up", "name": "sign up", "type": "events", "order": 0,},
                            {"id": "no events"},
                        ],
                    }
                ),
                self.team,
            )
        self.assertEqual(response[0]["label"], "sign up - value")
        self.assertEqual(response[1]["label"], "sign up - other_value")
        self.assertEqual(response[2]["label"], "no events - value")
        self.assertEqual(response[3]["label"], "no events - other_value")
        self.assertEqual(sum(response[0]["data"]), 2)
        self.assertEqual(response[0]["breakdown_value"], "value")
        self.assertEqual(sum(response[1]["data"]), 1)
        self.assertEqual(response[1]["breakdown_value"], "other_value")
    def test_breakdown_filtering_with_properties(self):