fix: panic in MarshalToSizedBuffer on optional fields

[lklimek]

When using protoc-gen-gogofaster with proto3 optional fields, I get panic in MarshalToSizedBuffer:

panic: runtime error: invalid memory address or nil pointer dereference

Full proto3 message definition can be found here, important part:

message ValidatorParams {
  optional uint64 voting_power_threshold = 2;  //[(gogoproto.nullable) = true]
}

Solution

Added check if message to marshal is nil.

Logs

github.com/dashpay/tenderdash/proto/tendermint/types.(*ValidatorParams_VotingPowerThreshold).MarshalToSizedBuffer(...)
        tenderdash/proto/tendermint/types/params.pb.go:1323
github.com/dashpay/tenderdash/proto/tendermint/types.(*ValidatorParams_VotingPowerThreshold).MarshalTo(0x0, {0xc0004a6960, 0xc0004a6966?, 0x33})
        tenderdash/proto/tendermint/types/params.pb.go:1318 +0x8e
github.com/dashpay/tenderdash/proto/tendermint/types.(*ValidatorParams).MarshalToSizedBuffer(0xc0006819e0, {0xc0004a6930, 0x30, 0x63})
        tenderdash/proto/tendermint/types/params.pb.go:1299 +0x126
github.com/dashpay/tenderdash/proto/tendermint/types.(*ConsensusParams).MarshalToSizedBuffer(0xc000147e20, {0xc0004a6930, 0x61, 0x63})
        tenderdash/proto/tendermint/types/params.pb.go:1164 +0x5b5
github.com/dashpay/tenderdash/proto/tendermint/state.(*ConsensusParamsInfo).MarshalToSizedBuffer(0xc000147e20, {0xc0004a6930, 0x63, 0x63})
        tenderdash/proto/tendermint/state/types.pb.go:579 +0xea