[Bug]: `TldrawUi` crashes when `embed` shape util is not provided
### What happened?

I am trying to implement [exploded example](https://tldraw.dev/examples/editor-api/exploded) and omit most of default shapes.
But when `embed` shape not included `TldrawUi` breaks. Seems that the reason for that is `useGetEmbedShapeUtil` assume that `embed` shape might be empty, but `Editor.getShapeUtil` that used in this function throws if shape is not found.

```
Editor.mjs:838 Uncaught Error: No shape util found for type "embed"
    at Editor.getShapeUtil (Editor.mjs:838:1)
    at useGetEmbedShapeUtil (useGetEmbedDefinition.mjs:4:1)
    at useGetEmbedDefinition (useGetEmbedDefinition.mjs:7:1)
    at useDefaultHelpers (overrides.mjs:23:1)
    at useMergedOverrides (overrides.mjs:122:1)
    at InternalProviders (TldrawUiContextProvider.mjs:43:1)
    at renderWithHooks (react-dom.development.js:15486:1)
    at mountIndeterminateComponent (react-dom.development.js:20103:1)
    at beginWork (react-dom.development.js:21626:1)
    at HTMLUnknownElement.callCallback (react-dom.development.js:4164:1)
```

### How can we reproduce the bug?

- Load [exploded example](https://tldraw.dev/examples/editor-api/exploded)
- Remove `EmbedShapeUtil` from list of `defaultShapeUtils`
- `TldrawUi` throws an error

### What browsers are you seeing the problem on?

Firefox, Chrome, Safari, Microsoft Edge

### Where did this happen?

The developer package

### Contact Details

_No response_

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