Web UI: fails rendering archived repository with 500 error "directory"

Browsing this repo:

• https://archive.softwareheritage.org/browse/origin/https://github.com/ska-sa/PySPEAD/directory/

fails with a 500 HTTP error and message 'directory'. The repository has been ingested recently and seems to still exist upstream.

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Migrated from T1309 (view on Phabricator)