What happens when we interleave two threads, one calling GetPubKey() and the other RemoveWatchKey()? GetPubKey() has no locks, so if we call RemoveWatchKey() after `if (it != mapWatchKeys.end()) //line23` and before `vchPubKeyOut = it->second; //line24` there is going to be a problem.

#include "keystore.h"
#include "key.h"
#include "pubkey.h"
#include "util.h"
#include <boost/foreach.hpp>
bool CKeyStore::AddKey(const CKey &key) {
    return AddKeyPubKey(key, key.GetPubKey());
}
bool CBasicKeyStore::GetPubKey(const CKeyID &address, CPubKey &vchPubKeyOut) const
{
    CKey key;
    if (!GetKey(address, key)) {
        WatchKeyMap::const_iterator it = mapWatchKeys.find(address);
        if (it != mapWatchKeys.end()) {
            vchPubKeyOut = it->second;
            return true;
        }
        return false;
    }
    vchPubKeyOut = key.GetPubKey();
    return true;
}
bool CBasicKeyStore::AddKeyPubKey(const CKey& key, const CPubKey &pubkey)