fix error with genesis event being nil

Author: jonastheis

rollup/da_syncer/da/calldata_blob_source.go

@@ -197,7 +197,7 @@ func (ds *CalldataBlobSource) getCommitBatchDA(commitEvents []*l1.CommitBatchEve
 	}
 
 	if commitEvents[0].BatchIndex().Uint64() == 0 {
-		return Entries{NewCommitBatchDAV0Empty()}, nil
+		return Entries{NewCommitBatchDAV0Empty(commitEvents[0])}, nil
 	}
 
 	firstCommitEvent := commitEvents[0]

rollup/da_syncer/da/commitV0.go

@@ -66,9 +66,10 @@ func NewCommitBatchDAV0WithChunks(db ethdb.Database,
 	}, nil
 }
 
-func NewCommitBatchDAV0Empty() *CommitBatchDAV0 {
+func NewCommitBatchDAV0Empty(event *l1.CommitBatchEvent) *CommitBatchDAV0 {
 	return &CommitBatchDAV0{
 		batchIndex: 0,
+		event:      event,
 	}
 }