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 (!gArgs.GetBoolArg("-rescan", false))
    {
        WalletBatch batch(*walletInstance->database);
        CBlockLocator locator;
        if (batch.ReadBestBlock(locator)) {
            if (const Optional<int> fork_height = locked_chain->findLocatorFork(locator)) {
                rescan_height = *fork_height;
            }
        }
    }
    const Optional<int> tip_height = locked_chain->getHeight();
    if (tip_height) {
        walletInstance->m_last_block_processed = locked_chain->getBlockHash(*tip_height);
        walletInstance->m_last_block_processed_height = *tip_height;
    } else {
        walletInstance->m_last_block_processed.SetNull();
        walletInstance->m_last_block_processed_height = -1;
    }
    if (tip_height && *tip_height != rescan_height)
    {
        
        
        
        if (chain.havePruned()) {
            
            
            
            int block_height = *tip_height;
            while (block_height > 0 && locked_chain->haveBlockOnDisk(block_height - 1) && rescan_height != block_height) {
                --block_height;