Problem: rpc server handler crash when the rpc call send_transaction missing the gas related arguments

[JayT106]

System info: [Include Ethermint commit, operating system name, and other relevant details]

__Steps to reproduce:

When I was fixing the rpc-test with main branch, 202bc5f
some tests are missing the gas info in the sending param.
i.e.
TestEth_SendTransaction_ContractDeploy
When running these tests against ethermintd, we can see the ERR msg on the server-side.

4:11PM ERR Failed to read request err="websocket: close 1006 (abnormal closure): unexpected EOF" module=rpc-server protocol=websocket remote={"IP":"127.0.0.1","Port":64346,"Zone":""} server=node

And the test case failed with the message

Expected nil, but got: &rpc.Error{Code:-32000, Message:"method handler crashed", Data:interface {}(nil)}

__Expected behavior:
The rpc server should handle the eth_sendTransaction with missing tx arguments

__Additional info:
issue happens when working on
#608