The function buf_page_free() that was introduced
in commit a35b4ae8 (MDEV-15528)
failed to remove any adaptive hash index entries for the page
before freeing the page.

This caused an assertion failure on shutdown of 10.6 server of
in the function buf_pool_t::clear_hash_index() with the expression:
(s >= buf_page_t::UNFIXED || s == buf_page_t::REMOVE_HASH).
The assertion would fail for a block that is in the freed state.

The failing assertion was added in
commit aaef2e1d
in the 10.6 branch.

Thanks to Matthias Leich for finding the bug and testing the fix.