Funnels built in the visualizer are broken in subscriptions

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### Describe the bug

In the visualizer, you can build a funnel from several individual number cards. When such a funnel is included in a dashboard subscription, the email shows "An error has occurred while displaying this card".

Questions with funnel viz type for fine - the issue is restricted to funnels built from number cards

### To Reproduce

1. Create several questions returning a single number, e.g Count of Orders, Count of Orders/2, and Count of Orders/3
2. Create a new dashboard.
3. Add one of the number questions to the dashboard.
4. Click "Visualize another way" on the card to open the visualizer.
5. In the visualizer, click on Add more data in the left sidebar.
6. Search for and add remaining questions.
8. Switch visualization to Funnel.

10. Save. the visualization and the dashboard

12. Set up a dashboard subscription and click "Send email now" to test it.

### Expected behavior

Subscription contains the funnel image

### Logs

_No response_

### Information about your Metabase installation

```JSON
62.3.5 but probably been there for a couple of releases
```

### Severity

P2

### Additional context

_No response_

Start by reproducing the issue from the visualizer entry point, then trace how a dashboard subscription renders a funnel built from multiple number cards. Use “Send email now” to verify the failure and compare it with a funnel visualization question; done means the subscription email contains the funnel image instead of the error message.

Written by the indexing model from the issue text.