replayer crashes on invalid directory entry name (b'gitter/gitter.xml')

https://sentry.softwareheritage.org/organizations/swh/issues/104802/?referrer=phabricator_plugin

ValueError: b'gitter/gitter.xml' is not a valid directory entry name.
(14 additional frame(s) were not displayed)
...
  File "swh/model/model.py", line 1195, in from_dict
    entries=tuple(
  File "swh/model/model.py", line 1196, in <genexpr>
    DirectoryEntry.from_dict(entry) for entry in d.pop("entries")
  File "swh/model/model.py", line 352, in from_dict
    return cls(**d)
  File "<attrs generated init swh.model.model.DirectoryEntry>", line 7, in __init__
    Implementation of Software Heritage's data model
  File "swh/model/model.py", line 1163, in check_name
    raise ValueError(f"{value!r} is not a valid directory entry name.")

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Migrated from T4644 (view on Phabricator)