Merge #18274: rpc/wallet: initialize nFeeRequired to avoid using garbage value on failure

a652ba6293 rpc/wallet: initialize nFeeRequired to avoid using garbage value on failure (Karl-Johan Alm)

Pull request description:

  Initialize the `nFeeRequired` variable to avoid using an uninitialized value for errors happening before it is set to 0.

  Note: this originally fixed `nFeeRet` in `wallet.cpp`.

ACKs for top commit:
  promag:
    ACK a652ba6293.
  Sjors:
    utACK a652ba6293
  practicalswift:
    ACK a652ba6293 -- patch looks correct
  meshcollider:
    utACK a652ba6293

Tree-SHA512: 0d12f1ffd0851ed5ce6d109d2c87f55e8b1d57da297e684feeabb57229200c4078f029c55ca5aa5712bd18e26dda3ce538443dfe68a7a6d504428068f81fded0

src/wallet/rpcwallet.cpp

@@ -343,7 +343,7 @@ static CTransactionRef SendMoney(interfaces::Chain::Lock& locked_chain, CWallet
     CScript scriptPubKey = GetScriptForDestination(address);
 
     // Create and send the transaction
-    CAmount nFeeRequired;
+    CAmount nFeeRequired = 0;
     std::string strError;
     std::vector<CRecipient> vecSend;
     int nChangePosRet = -1;