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
"date_from": (now - timedelta(1)).strftime(FORMAT_TIME),
                "date_to": now.strftime(FORMAT_TIME_DAY_END),
                "funnel_window_days": 1,
                "events": [
                    {"id": "step one", "order": 0},
                    {"id": "step two", "order": 1},
                    {"id": "step three", "order": 2},
                ],
            }
        )
        results = ClickhouseFunnelTrends(filter, self.team, ClickhouseFunnel)._exec_query()
        self.assertEqual(len(results), 2)
        day = results[0]  
        self.assertEqual(day["reached_from_step_count"], 0)
        self.assertEqual(day["reached_to_step_count"], 0)
        self.assertEqual(day["conversion_rate"], 0)
        self.assertEqual(
            day["timestamp"].replace(tzinfo=pytz.UTC),
            (datetime(now.year, now.month, now.day) - timedelta(1)).replace(tzinfo=pytz.UTC),
        )
        self.assertEqual(day["is_period_final"], True)  
        day = results[1]  
        self.assertEqual(day["reached_from_step_count"], 1)
        self.assertEqual(day["reached_to_step_count"], 1)
        self.assertEqual(day["conversion_rate"], 100)
        self.assertEqual(
            day["timestamp"].replace(tzinfo=pytz.UTC), datetime(now.year, now.month, now.day).replace(tzinfo=pytz.UTC)
        )
        self.assertEqual(day["is_period_final"], False)  
    def test_two_runs_by_single_user_in_one_period(self):