Return appropriate error code when there's no connection to daemon

src/wallet/wallet_rpc_server.cpp

@@ -2397,6 +2397,11 @@ namespace tools
     {
       std::rethrow_exception(e);
     }
+    catch (const tools::error::no_connection_to_daemon& e)
+    {
+      er.code = WALLET_RPC_ERROR_CODE_NO_DAEMON_CONNECTION;
+      er.message = e.what();
+    }
     catch (const tools::error::daemon_busy& e)
     {
       er.code = WALLET_RPC_ERROR_CODE_DAEMON_IS_BUSY;

src/wallet/wallet_rpc_server_error_codes.h

@@ -68,3 +68,4 @@
 #define WALLET_RPC_ERROR_CODE_MULTISIG_SIGNATURE     -35
 #define WALLET_RPC_ERROR_CODE_MULTISIG_SUBMISSION    -36
 #define WALLET_RPC_ERROR_CODE_NOT_ENOUGH_UNLOCKED_MONEY -37
+#define WALLET_RPC_ERROR_CODE_NO_DAEMON_CONNECTION   -38