## Bug description
I added an event (that exists) to an action, and now my action hangs forever.

I added an insight viewed event

w/ filters `insight == RETENTION` and `same_retention_and_cohortizing_event = false` – this appears to have broken my action where it does not load and I cannot edit it.

Cannot reproduce this same behavior locally.


## Expected behavior
- The action loads if the schema is correct.
-  If there's erroneous data it should load and let me edit it.

## How to reproduce

1. Create an action on Posthog cloud, in our main app
2. Add 'insight viewed' with filters `insight == RETENTION` and `same_retention_and_cohortizing_event = false`
3. The action will spin forever

## Environment

- [x] PostHog Cloud
- [ ] self-hosted PostHog, version/commit: _please provide_

## Additional context

[Sentry error](https://sentry.io/organizations/posthog/issues/2378948964/?project=1899813&referrer=slack)

Console errors 
<img width="1607" alt="Screen Shot 2021-05-03 at 5 45 39 PM" src="https://user-images.githubusercontent.com/5965891/116950024-b0d7a280-ac38-11eb-93c8-245390240532.png">
<img width="1167" alt="Screen Shot 2021-05-03 at 5 51 34 PM" src="https://user-images.githubusercontent.com/5965891/116950026-b208cf80-ac38-11eb-96e1-6a8f018f650a.png">



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

ee/clickhouse/views/actions.py
and isinstance(filter.breakdown_value, str)
    ):
        person_prop = Property(**{"key": filter.breakdown, "value": filter.breakdown_value, "type": "person"})
        filter.properties.append(person_prop)
    prop_filters, prop_filter_params = parse_prop_clauses(
        filter.properties, team.pk, filter_test_accounts=filter.filter_test_accounts
    )
    params: Dict = {"team_id": team.pk, **prop_filter_params, **entity_params, "offset": filter.offset}
    if entity.math in [WEEKLY_ACTIVE, MONTHLY_ACTIVE]:
        active_user_params = get_active_user_params(filter, entity, team.pk)
        content_sql = PERSONS_ACTIVE_USER_SQL.format(
            entity_query=f"AND {entity_sql}",
            parsed_date_from=parsed_date_from,
            parsed_date_to=parsed_date_to,
            filters=prop_filters,
            breakdown_filter="",
            person_filter=person_filter,
            **active_user_params,
        )
    else:
        content_sql = PERSON_TREND_SQL.format(
            entity_filter=f"AND {entity_sql}",
            parsed_date_from=parsed_date_from,
            parsed_date_to=parsed_date_to,
            filters=prop_filters,
            breakdown_filter="",
            person_filter=person_filter,
        )
    return content_sql, {**params, **person_filter_params}
def calculate_entity_people(team: Team, entity: Entity, filter: Filter):