Sentry Issue: [POSTHOG-37H](https://sentry.io/organizations/posthog/issues/2511149053/?referrer=github_integration)

```
AttributeError: 'NoneType' object has no attribute 'strftime'
(3 additional frame(s) were not displayed)
...
  File "ee/clickhouse/views/insights.py", line 90, in calculate_funnel
    "result": ClickhouseFunnelTrends(team=team, filter=filter, funnel_order_class=funnel_order_class).run()
  File "ee/clickhouse/queries/funnels/base.py", line 48, in run
    results = self._exec_query()
  File "ee/clickhouse/queries/funnels/funnel_trends.py", line 61, in _exec_query
    return self._summarize_data(super()._exec_query())
  File "ee/clickhouse/queries/funnels/base.py", line 118, in _exec_query
    query = self.get_query()
  File "ee/clickhouse/queries/funnels/funnel_trends.py", line 112, in get_query
    {interval_method}(toDateTime('{self._filter.date_from.strftime(TIMESTAMP_FORMAT)}') + number * {seconds_in_interval}) AS entrance_period_start
```
ee/clickhouse/queries/funnels/test/test_funnel_trends.py
from datetime import datetime, timedelta
from uuid import uuid4
import pytz
from ee.clickhouse.models.event import create_event
from ee.clickhouse.queries.funnels import ClickhouseFunnel, ClickhouseFunnelStrict, ClickhouseFunnelUnordered
from ee.clickhouse.queries.funnels.funnel_trends import ClickhouseFunnelTrends
from ee.clickhouse.queries.funnels.funnel_trends_persons import ClickhouseFunnelTrendsPersons
from ee.clickhouse.util import ClickhouseTestMixin
from posthog.constants import INSIGHT_FUNNELS, TRENDS_LINEAR
from posthog.models.cohort import Cohort
from posthog.models.filters import Filter
from posthog.models.person import Person
from posthog.test.base import APIBaseTest
FORMAT_TIME = "%Y-%m-%d %H:%M:%S"
FORMAT_TIME_DAY_END = "%Y-%m-%d 23:59:59"
def _create_person(**kwargs):
    person = Person.objects.create(**kwargs)
    return Person(id=person.uuid, uuid=person.uuid)
def _create_event(**kwargs):
    kwargs.update({"event_uuid": uuid4()})
    create_event(**kwargs)
class TestFunnelTrends(ClickhouseTestMixin, APIBaseTest):