fix: TimeIotaMs must be strictly positive (#1872)

Implements
celestiaorg/celestia-app#4888 (comment)

## Testing
- [x] State sync a node on Mocha using v4.x
- [x] Create a v3.x celestia-app binary that uses this PR
- [x] Downgrade to the v3.x binary on the Mocha node. Confirm it can
continue running

## Follow ups

- [ ] Create a v0.34.x-celestia release
- [ ] Bump in v3.x on celestia-app
- [ ] Create another v3.x celestia-app release
- [ ]  Re-test downgrading from v4.x to v3.x

Author: rootulp

types/params.go

@@ -89,9 +89,8 @@ func ValidateConsensusParams(params cmtproto.ConsensusParams) error {
 			params.Block.MaxGas)
 	}
 
-	if params.Block.TimeIotaMs <= 0 {
-		return fmt.Errorf("block.TimeIotaMs must be greater than 0. Got %v",
-			params.Block.TimeIotaMs)
+	if params.Block.TimeIotaMs < 0 {
+		return fmt.Errorf("block.TimeIotaMs must be positive. Got %v", params.Block.TimeIotaMs)
 	}
 
 	if params.Evidence.MaxAgeNumBlocks <= 0 {

types/params_test.go

@@ -32,15 +32,16 @@ func TestConsensusParamsValidation(t *testing.T) {
 		6: {makeParams(1024*1024*1024, 0, 10, 2, 0, valEd25519), false},
 		7: {makeParams(1024*1024*1024, 0, 10, -1, 0, valEd25519), false},
 		8: {makeParams(1, 0, -10, 2, 0, valEd25519), false},
+		9: {makeParams(1, 0, 0, 2, 0, valEd25519), true}, // 0 is a valid time iota ms
 		// test evidence params
-		9:  {makeParams(1, 0, 10, 0, 0, valEd25519), false},
-		10: {makeParams(1, 0, 10, 2, 2, valEd25519), false},
-		11: {makeParams(1000, 0, 10, 2, 1, valEd25519), true},
-		12: {makeParams(1, 0, 10, -1, 0, valEd25519), false},
+		10: {makeParams(1, 0, 10, 0, 0, valEd25519), false},
+		11: {makeParams(1, 0, 10, 2, 2, valEd25519), false},
+		12: {makeParams(1000, 0, 10, 2, 1, valEd25519), true},
+		13: {makeParams(1, 0, 10, -1, 0, valEd25519), false},
 		// test no pubkey type provided
-		13: {makeParams(1, 0, 10, 2, 0, []string{}), false},
+		14: {makeParams(1, 0, 10, 2, 0, []string{}), false},
 		// test invalid pubkey type provided
-		14: {makeParams(1, 0, 10, 2, 0, []string{"potatoes make good pubkeys"}), false},
+		15: {makeParams(1, 0, 10, 2, 0, []string{"potatoes make good pubkeys"}), false},
 	}
 	for i, tc := range testCases {
 		if tc.valid {