TypeError: color.charCodeAt is not a function when using github-dark-default with @shikijs/monaco

[MathiasWP]

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Describe the bug

I have this shiki setup:

import { shikiToMonaco } from '@shikijs/monaco';
import { bundledLanguagesInfo, createHighlighter } from 'shiki';

export async function registerShiki(monaco: typeof Monaco) {
	const highlighter = await createHighlighter({
		themes: ['github-dark-default'],
		langs: bundledLanguagesInfo.map(lang => lang.id) // This isn't very performant, but shouldn't all of these work?
	});

	const languagesAlreadyInMonaco = monaco.languages.getLanguages();
	for (const language of bundledLanguagesInfo.filter((language) => !languagesAlreadyInMonaco.some((l) => l.id === language.id))) {
		monaco.languages.register({ id: language.id });
	}

	shikiToMonaco(highlighter, monaco);
}

If i github-dark-default as a theme i get the following error in my console:

It works fine if i set github-dark as my theme. What am i doing wrong here?

Reproduction

look at code example

Contributes

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests