Both grids restored the last good filter by recursing into the filter handler, which
never terminated once the search index rather than the query was the problem: the
restore fails the same way, and the retry uses the same filter. The user got an
endless run of dialogs, each of them blaming a filter string that was fine. Only an
empty last-good filter broke the loop, because that short-circuits before reaching
the search engine.
The fallback is now a bounded sequence -- last good filter, then no filter -- and
the message distinguishes an index Libation cannot reach from a query it cannot
parse. Only the first failure is reported, so restoring is quiet. A malformed query
never surfaces as an IO-family exception, which QueryFailureShapeTests pins against
the real engine, so a typo is never mistaken for index trouble or made to trigger a
rebuild.
Co-authored-by: rmcrackan <rmcrackan@gmail.com>
