do not write batches to the stream with a missing fork id (erigontech…

…#614)

zk/datastream/server/data_stream_server.go

@@ -239,9 +239,11 @@ func (srv *DataStreamServer) CreateStreamEntriesProto(
 		entryCount += 2
 
 		// a gap of 1 is normal but if greater than we need to account for the empty batches which will each
-		// have a batch bookmark, batch start and batch end - but only if we're operating pre-etrog
+		// have a batch bookmark, batch start and batch end - but only if we're operating pre-etrog and the
+		// fork exists (i.e. not 0)
 		for i := lastBatchNumber + 1; i < batchNumber; i++ {
-			if batchesToForks[i] < EtrogBatchNumber {
+			fork := batchesToForks[i]
+			if fork != 0 && fork < EtrogBatchNumber {
 				entryCount += 3
 			}
 		}
@@ -261,9 +263,11 @@ func (srv *DataStreamServer) CreateStreamEntriesProto(
 				workingBatch := lastBatchNumber + uint64(i)
 
 				// check the fork of the batch being skipped - if it is etrog+ then we can skip this
-				// as we don't want empty batches there
+				// as we don't want empty batches there - a 0 fork here would indicate that the batch
+				// was not in the parent stream (bad batch) so we want to skip it in our own production
+				// of the stream
 				workingFork := batchesToForks[workingBatch]
-				if workingFork >= EtrogBatchNumber {
+				if workingFork == 0 || workingFork >= EtrogBatchNumber {
 					continue
 				}