wallettool: Don't unilaterally reset wallet_instance if loading error

When there is a wallet loading error, it could be a noncritical one so
it is not necessary to make wallet_instance a nullptr. The wallet can
still go on with normal operation in that case, as we do for loading in
bitcoind and bitcoin-qt.

src/wallet/wallettool.cpp

@@ -68,7 +68,6 @@ static std::shared_ptr<CWallet> MakeWallet(const std::string& name, const fs::pa
     }
 
     if (load_wallet_ret != DBErrors::LOAD_OK) {
-        wallet_instance = nullptr;
         if (load_wallet_ret == DBErrors::CORRUPT) {
             tfm::format(std::cerr, "Error loading %s: Wallet corrupted", name);
             return nullptr;