Avoid leaking Index.aiRowEst memory if an OOM causes a rollback which deletes

Avoid leaking Index.aiRowEst memory if an OOM causes a rollback which deletes
the index before the aiRowEst deletion code in sqlite3AnalysisLoad() routine
has a chance to run.  Since the aiRowEst now might be deleted from freeIndex()
which does not always have a db pointer, make sure the aiRowEst memory is
not held in lookaside.

FossilOrigin-Name: efd87ba142723ba131fcc985db6eb45c5a3c637b