validation: prevent FindMostWorkChain from causing UB#317

1440000bytes wants to merge 2 commits into

bitcoinknots:29.x-knotsbitcoinknots/bitcoin:29.x-knotsfrom

1440000bytes:fix/blocks-unlinked-ub-350701440000bytes/bitcoin:fix/blocks-unlinked-ub-35070Copy head branch name to clipboard