(check-in [0057bbb508e7662b] about 16 hours ago), be sure
to clear the BTCF_ValidOvfl flag, since the overflow cache is invalidated
by the search on the last page. OSSFuzz issue 45329.
FossilOrigin-Name: 0021bebc162e001b788786703ce634e7b8fcd3976f7047a5956e82140791e765