Fix fallback build number retrieval again

[edpowers]

Summary

Fixes breaking issue where the .js asset paths aren't being parsed

General Info

• [ ] If code changes were made then they have been tested.
  • [ ] I have updated the documentation to reflect the changes.
• [X] This PR fixes an issue (please put issue # in summary).
• [ ] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)