Bug: 'Invalid url' for newly added images

[Jwaegebaert]

When a new image is added for a sample and used in the docs, the validator will fail, stating "Invalid URL for thumbnail pnp/cli-microsoft365#1 property: The provided URL is not responding correctly!" This doesn't seem like intended behavior. New images and their related URLs shouldn't cause validation to fail.

Additionally, the failure message references the faulty property location as #1, which causes GitHub to link to an unrelated issue. This also doesn't appear as intended.

Ref: pnp/cli-microsoft365#6027 (comment)