`useImage` hook throws an error in `data.getRaster` when image selection is changed

[xinaesthete]

I'd mostly ignored this as it seemed to not have any major detrimental effect beyond a console.error being logged - but I think when embedded in docusaurus it presents a large "Uncaught runtime errors" overlay.

Note that MDV doesn't have an error when doing similar image switching (and pretty sure Avivator doesn't either). In MDV, the way it works when changing via chart settings GUI is that the config.region value is mutated, which eventually surfaces via useImgUrl() / useRegion() and mobx observing that mutation... Not entirely sure what is wrong about the element/loader changing logic here but essentially when we

  const source = useViewerStore((state) => state.source);
  useImage(source);

That seems to be using an empty source before loader is quite ready yet.

[xinaesthete]

It has source = [{labels: [], shape: []}] when the problem occurs.