types: check if nil or empty valset (#5167)

Solves #5138 in the way that if a validatorSet is nil or empty it will not try to transform it to protobug

Co-authored-by: Callum Michael Waters <cmwaters19@gmail.com>

consensus/byzantine_test.go

@@ -167,7 +167,7 @@ func TestByzantinePrevoteEquivocation(t *testing.T) {
 		msg := <-blocksSubs[j].Out()
 		block := msg.Data().(types.EventDataNewBlock).Block
 		// assert that we have evidence
-		assert.True(t, len(block.Evidence.Evidence) == 1)
+		require.True(t, len(block.Evidence.Evidence) == 1)
 		// and that the evidence is of type DuplicateVoteEvidence
 		ev, ok := block.Evidence.Evidence[0].(*types.DuplicateVoteEvidence)
 		assert.True(t, ok)

state/state_test.go

@@ -1036,24 +1036,25 @@ func TestStateProto(t *testing.T) {
 	tc := []struct {
 		testName string
 		state    *sm.State
-		expPass  bool
+		expPass1 bool
+		expPass2 bool
 	}{
-		{"empty state", &sm.State{}, false},
-		{"nil failure state", nil, false},
-		{"success state", &state, true},
+		{"empty state", &sm.State{}, true, false},
+		{"nil failure state", nil, false, false},
+		{"success state", &state, true, true},
 	}
 
 	for _, tt := range tc {
 		tt := tt
 		pbs, err := tt.state.ToProto()
-		if !tt.expPass {
+		if !tt.expPass1 {
 			assert.Error(t, err)
 		} else {
 			assert.NoError(t, err, tt.testName)
 		}
 
 		smt, err := sm.StateFromProto(pbs)
-		if tt.expPass {
+		if tt.expPass2 {
 			require.NoError(t, err, tt.testName)
 			require.Equal(t, tt.state, smt, tt.testName)
 		} else {

types/validator_set.go

@@ -912,8 +912,8 @@ func (valz ValidatorsByAddress) Swap(i, j int) {
 
 // ToProto converts ValidatorSet to protobuf
 func (vals *ValidatorSet) ToProto() (*tmproto.ValidatorSet, error) {
-	if vals == nil {
-		return nil, errors.New("nil validator set") // validator set should never be nil
+	if vals.IsNilOrEmpty() {
+		return &tmproto.ValidatorSet{}, nil // validator set should never be nil
 	}
 
 	vp := new(tmproto.ValidatorSet)

types/validator_set_test.go

@@ -1598,8 +1598,8 @@ func TestValidatorSetProtoBuf(t *testing.T) {
 		{"fail valSet2, pubkey empty", valset2, false, false},
 		{"fail nil Proposer", valset3, false, false},
 		{"fail empty Proposer", valset4, false, false},
-		{"fail empty valSet", &ValidatorSet{}, false, false},
-		{"false nil", nil, false, false},
+		{"fail empty valSet", &ValidatorSet{}, true, false},
+		{"false nil", nil, true, false},
 	}
 	for _, tc := range testCases {
 		protoValSet, err := tc.v1.ToProto()