Keep the placeholder out of a cached scan

The cached list wrote "[no description]" like any other description,
so once read back it no longer counted as the placeholder and became
the meta description of every repository without one. Repositories
read back from the list are also marked as having had their
description file read, since the scan already did, so the index does
not open those files again on every request.

0 files changed, 0 insertions, 0 deletions