## 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/models/property.py
filters: List[Property],
    team_id: Optional[int],
    prepend: str = "global",
    table_name: str = "",
    allow_denormalized_props: bool = False,
    filter_test_accounts=False,
    is_person_query=False,
) -> Tuple[str, Dict]:
    final = []
    params: Dict[str, Any] = {}
    if team_id is not None:
        params["team_id"] = team_id
    if table_name != "":
        table_name += "."
    if filter_test_accounts:
        test_account_filters = Team.objects.only("test_account_filters").get(id=team_id).test_account_filters
        filters.extend([Property(**prop) for prop in test_account_filters])
    for idx, prop in enumerate(filters):
        if prop.type == "cohort":
            cohort = Cohort.objects.get(pk=prop.value, team_id=team_id)
            person_id_query, cohort_filter_params = format_filter_query(cohort)
            params = {**params, **cohort_filter_params}
            final.append(
                "AND {table_name}distinct_id IN ({clause})".format(table_name=table_name, clause=person_id_query)
            )
        elif prop.type == "person":
            filter_query, filter_params = prop_filter_json_extract(
                prop, idx, "{}person".format(prepend), allow_denormalized_props=allow_denormalized_props