@jonasschnelli wrote in #14979:
> #14573 broke < Qt5.6 compatibility due to calling the lambda version of `addAction` that was added in Qt5.6.

We currently [support](https://github.com/bitcoin/bitcoin/blob/master/doc/dependencies.md) QT >=5.2, but hardly anyone tests with that. If we make one of the Travis machines use it, we should have a better change of catching this.

See also discussion about minimum QT version in #13478 
if (result.status == ScanResult::FAILURE) {
            int64_t time_max;
            if (!chain().findBlock(result.failed_block, nullptr , nullptr , &time_max)) {
                throw std::logic_error("ScanForWalletTransactions returned invalid block hash");
            }
            return time_max + TIMESTAMP_WINDOW + 1;
        }
    }
    return startTime;
}
/**
 * Scan the block chain (starting in start_block) for transactions
 * from or to us. If fUpdate is true, found transactions that already
 * exist in the wallet will be updated.
 *
 * @param[in] start_block if not null, the scan will start at this block instead
 *            of the genesis block
 * @param[in] stop_block if not null, the scan will stop at this block instead
 *            of the chain tip
 *
 * @return ScanResult indicating success or failure of the scan. SUCCESS if
 * scan was successful. FAILURE if a complete rescan was not possible (due to
 * pruning or corruption). USER_ABORT if the rescan was aborted before it
 * could complete.
 *
 * @pre Caller needs to make sure start_block (and the optional stop_block) are on
 * the main chain after to the addition of any new keys you want to detect
 * transactions for.
 */
CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_block, const uint256& stop_block, const WalletRescanReserver& reserver, bool fUpdate)