fix(eslint-plugin): add optional chaining in no_css_color

[weronikaolejniczak]

Summary

Pipeline is failing at the linting stage on the PR: elastic/kibana#210082 because we're trying access init in undefined in the @elastic/eui/no-css-color.

Related to https://github.com/elastic/eui-private/issues/275

QA

1. Checkout this branch: gh pr checkout 8524
2. Build the ESLint plugin: yarn workspace @elastic/eslint-plugin-eui build
3. Publish locally: cd packages/eslint-plugin && yalc publish

Then, in Kibana:

1. Install the local ESLint plugin version: yalc add @elastic/eslint-plugin-eui
2. Reinstall dependencies: yarn kbn bootstrap --no-validate

Test files:

• src/platform/packages/shared/kbn-discover-utils/src/components/custom_control_columns/degraded_docs_control.tsx
• src/platform/plugins/shared/console/public/application/containers/editor/editor.tsx
• src/platform/plugins/shared/unified_search/public/saved_query_management/saved_query_management_list.tsx

There should be no errors in the ESLint output. Other warnings should display as appropriate.

[kibanamachine]

Preview staging links for this PR:

• Docs site: https://eui.elastic.co/pr_8524/
• Storybook: https://eui.elastic.co/pr_8524/storybook
• New docs: https://eui.elastic.co/pr_8524/new-docs

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 01138ca

cc @weronikaolejniczak