minor rework of SendMoney in rpcwallet

- rework the function to not log errors but use throw JSONRPCError
- remove a check for IsLocked() that is done in sendtoaddress and
  sendfrom RPC calls already
- cache GetBalance() return value, because it's possibly used twice

src/rpcwallet.cpp

@@ -19,6 +19,7 @@
 #include <stdint.h>
 
 #include <boost/assign/list_of.hpp>
+
 #include "json/json_spirit_utils.h"
 #include "json/json_spirit_value.h"
 
@@ -316,34 +317,28 @@ Value getaddressesbyaccount(const Array& params, bool fHelp)
     return ret;
 }
 
-void SendMoney(const CTxDestination &address, CAmount nValue, CWalletTx& wtxNew)
+static void SendMoney(const CTxDestination &address, CAmount nValue, CWalletTx& wtxNew)
 {
+    CAmount curBalance = pwalletMain->GetBalance();
+
     // Check amount
     if (nValue <= 0)
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid amount");
 
-    if (nValue > pwalletMain->GetBalance())
+    if (nValue > curBalance)
         throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Insufficient funds");
 
-    string strError;
-    if (pwalletMain->IsLocked())
-    {
-        strError = "Error: Wallet locked, unable to create transaction!";
-        LogPrintf("SendMoney(): %s", strError);
-        throw JSONRPCError(RPC_WALLET_ERROR, strError);
-    }
-
     // Parse Bitcoin address
     CScript scriptPubKey = GetScriptForDestination(address);
 
     // Create and send the transaction
     CReserveKey reservekey(pwalletMain);
     CAmount nFeeRequired;
-    if (!pwalletMain->CreateTransaction(scriptPubKey, nValue, wtxNew, reservekey, nFeeRequired, strError))
-    {
-        if (nValue + nFeeRequired > pwalletMain->GetBalance())
-            strError = strprintf("Error: This transaction requires a transaction fee of at least %s because of its amount, complexity, or use of recently received funds!", FormatMoney(nFeeRequired));
-        LogPrintf("SendMoney(): %s\n", strError);
+    std::string strError;
+    if (!pwalletMain->CreateTransaction(scriptPubKey, nValue, wtxNew, reservekey, nFeeRequired, strError)) {
+        if (nValue + nFeeRequired > curBalance)
+            throw JSONRPCError(RPC_WALLET_ERROR, strprintf("Error: This transaction requires a transaction fee of at least %s because of its amount, complexity, or use of recently received funds!", FormatMoney(nFeeRequired)));
+        else
             throw JSONRPCError(RPC_WALLET_ERROR, strError);
     }
     if (!pwalletMain->CommitTransaction(wtxNew, reservekey))