SS-1401 Address missing Github api token

[j-awada]

Description

Jira: https://scilifelab.atlassian.net/browse/SS-1401

E2E tests pass locally and fail on the GitHub workflow due to GHCR image validation issues. We suspect that the token is not set as an environment variable when the E2E tests run on GitHub.

Introduce code changes such that if the token is missing, do not validate the GHCR image.

Checklist

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• This pull request is against develop branch (not applicable for hotfixes)
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• I have included migration files (if there are changes to the model classes)
• I have included, reviewed and executed tests (unit and end2end) to complement my changes
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• In the case I have modified settings.py, then I have also updated the studio-settings-configmap.yaml file in serve-charts

[alfredeen]

Looks good!