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/funnel_trends.py
step_counts = self.get_step_counts_without_aggregation_query()
        # Ex
        self.params.update(self.funnel_order.params)
        reached_from_step_count_condition, reached_to_step_count_condition, _ = self.get_steps_reached_conditions()
        interval_method = get_trunc_func_ch(self._filter.interval)
        num_intervals, seconds_in_interval, _ = get_time_diff(
            self._filter.interval or "day", self._filter.date_from, self._filter.date_to, team_id=self._team.pk
        )
        breakdown_clause = self._get_breakdown_prop()
        query = f"""
            SELECT
                entrance_period_start,
                reached_from_step_count,
                reached_to_step_count,
                if(reached_from_step_count > 0, round(reached_to_step_count / reached_from_step_count * 100, 2), 0) AS conversion_rate
                {breakdown_clause}
            FROM (
                SELECT
                    entrance_period_start,
                    countIf({reached_from_step_count_condition}) AS reached_from_step_count,
                    countIf({reached_to_step_count_condition}) AS reached_to_step_count
                    {breakdown_clause}
                FROM (