PDF embedder not working with CDN on a multisite

PDF embedder is not working on a subsite with a mapped domain when Hummingbird’s CDN is enabled.

Setting up fake worker failed: “Cannot load script at: https://hb.wpmucdn.com/maindomain.com/7dbbe323-89fa-4a0b-9699-9dd4e16ac6f6.worker.js”.