add catch for rpc error

[taunusbb]

JsonRpcEngine: Response has no error or result for request: { "id": "f759a3f2-66cf-4053-b498-2913a179c4b6", "jsonrpc": "2.0", "method": "eth_getTransactionCount", "params": [ "0x6097ffc8d5e54de24b2a8a1d21df054b17990399", "0x138b731" ] }