fix(consensus): handle nil quorum on different round and enable proto…

…buf nil votes

crates/papyrus_protobuf/src/converters/consensus.rs

@@ -77,11 +77,8 @@ impl TryFrom<protobuf::Vote> for Vote {
 
         let height = value.height;
         let round = value.round;
-        let block_hash: StarkHash = value
-            .block_hash
-            .ok_or(ProtobufConversionError::MissingField { field_description: "block_hash" })?
-            .try_into()?;
-        let block_hash = Some(BlockHash(block_hash));
+        let block_hash: Option<BlockHash> =
+            value.block_hash.map(|block_hash| block_hash.try_into()).transpose()?.map(BlockHash);
         let voter = value
             .voter
             .ok_or(ProtobufConversionError::MissingField { field_description: "voter" })?

crates/sequencing/papyrus_consensus/src/state_machine.rs

@@ -333,8 +333,13 @@ impl StateMachine {
         if *count < self.quorum {
             return VecDeque::new();
         }
-        if block_hash.is_none() && round == self.round {
-            return self.advance_to_round(round + 1, leader_fn);
+        if block_hash.is_none() {
+            if round == self.round {
+                return self.advance_to_round(round + 1, leader_fn);
+            } else {
+                // NIL quorum reached on a different round.
+                return VecDeque::new();
+            }
         }
         let Some(proposed_value) = self.proposals.get(&round) else {
             return VecDeque::new();