Opening two of the same wallet (tested in v0.18.0 of bitcoin-qt 64 bit) will cause a database collision, and will crash the program.

`[marshall@likon] {21:21} [~] $ bitcoin-0.18.0/bin/bitcoin-qt `
`terminate called after throwing an instance of 'std::runtime_error'  what():  BerkeleyBatch: Can't open database 8204388-wallet.dat (duplicates fileid 8b1c090000000800e25686350000000000000000 from 1352491-wallet.dat)`
`Aborted (core dumped)`

I have been able to reproduce the issue by importing two of the same wallet (with different filenames).
if (!chain().findBlock(result.last_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 Scan starting block. If block is not on the active
 *                        chain, the scan will return SUCCESS immediately.
 * @param[in] stop_block  Scan ending block. If block is not on the active
 *                        chain, the scan will continue until it reaches the
 *                        chain tip.
 *
 * @return ScanResult returning scan information and indicating success or
 *         failure. Return status will be set to 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)