## Bug description

From [a customer report](https://posthoghelp.zendesk.com/agent/tickets/653):

```
I'm accessing insight results through the API, and I’ve noticed that sometimes the result is null in the response.
When I go and view the insight in Posthog and tap “refresh” the result starts to return in the API response.
I’ve also noticed there is a “refreshing” boolean flag in the insight response.
How do I set the insight to either refresh periodically or on request so I always get a result through the API?
```

It seems like the insight returns null if it's not refreshed manually from the frontend.

## How to reproduce

1. Call an insight with GET | /api/projects/:project_id/insights/:id
2. Response is `null`
3. Refresh the insight from the frontend
4. Response is populated

## Environment

- [ ] PostHog Cloud
- [ ] self-hosted PostHog, version/commit: please provide

## Additional context


posthog/api/insight.py
#
    
    
    
    
    #
    
    
    
    
    
    @extend_schema(
        request=TrendSerializer,
        methods=["POST"],
        tags=["trend"],
        operation_id="Trends",
        responses=TrendResultsSerializer,
    )
    @action(methods=["GET", "POST"], detail=False)
    def trend(self, request: request.Request, *args: Any, **kwargs: Any):
        try:
            serializer = TrendSerializer(request=request)
            serializer.is_valid(raise_exception=True)
        except Exception as e:
            capture_exception(e)
        result = self.calculate_trends(request)