`bitcoin-cli loadwallet "wallet.dat"` command causes bitcoind crash

log info:
```
bitcoind: wallet/db.cpp:236: BerkeleyEnvironment::VerifyResult BerkeleyEnvironment::Verify(const string&, BerkeleyEnvironment::recoverFunc_type, std::__cxx11::string&): Assertion `mapFileUseCount.count(strFile) == 0' failed.
Aborted (core dumped)
```

Bitcoin Core Daemon version `v0.17.0.0-ge1ed37edaedc85b8c3468bd9a726046344036243`

{
            boost::this_thread::interruption_point();
            std::map<std::string, int>::iterator mi = env->mapFileUseCount.find(strFile);
            if (mi != env->mapFileUseCount.end())
            {
                LogPrint(BCLog::DB, "Flushing %s\n", strFile);
                int64_t nStart = GetTimeMillis();
                
                env->CloseDb(strFile);
                env->CheckpointLSN(strFile);
                env->mapFileUseCount.erase(mi++);
                LogPrint(BCLog::DB, "Flushed %s %dms\n", strFile, GetTimeMillis() - nStart);
                ret = true;
            }
        }
    }
    return ret;
}
bool BerkeleyDatabase::Rewrite(const char* pszSkip)
{
    return BerkeleyBatch::Rewrite(*this, pszSkip);
}
bool BerkeleyDatabase::Backup(const std::string& strDest)
{
    if (IsDummy()) {
        return false;
    }
    while (true)
    {
        {