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
count = len(summary)
        data = []
        days = []
        labels = []
        for row in summary:
            data.append(row["conversion_rate"])
            hour_min_sec = " %H:%M:%S" if self._filter.interval == "hour" or self._filter.interval == "minute" else ""
            days.append(row["timestamp"].strftime(f"%Y-%m-%d{hour_min_sec}"))
            labels.append(row["timestamp"].strftime(HUMAN_READABLE_TIMESTAMP_FORMAT))
        return {
            "count": count,
            "data": data,
            "days": days,
            "labels": labels,
        }
    def _is_period_final(self, timestamp: Union[datetime, date]):
        # di
        now = datetime.utcnow().date()
        intervals_to_subtract = self._filter.funnel_window_interval * -1
        interval_unit = (
            "day" if self._filter.funnel_window_interval_unit is None else self._filter.funnel_window_interval_unit
        )
        delta = relativedelta(**{f"{interval_unit}s": intervals_to_subtract})
        completed_end = now + delta
        compare_timestamp = timestamp.date() if isinstance(timestamp, datetime) else timestamp
        is_final = compare_timestamp <= completed_end
        return is_final