chore: use proto Getter functions instead of fields (that are potenti…

…ally nil)

verify/verifier.go

@@ -76,7 +76,7 @@ func (v *Verifier) VerifyCert(ctx context.Context, cert *Certificate) error {
 	}
 
 	// 3 - verify security parameters
-	batchHeader := cert.Proof().BatchMetadata.BatchHeader
+	batchHeader := cert.Proof().GetBatchMetadata().GetBatchHeader()
 	err = v.verifySecurityParams(cert.ReadBlobHeader(), batchHeader.QuorumNumbers, batchHeader.QuorumSignedPercentages)
 	if err != nil {
 		return fmt.Errorf("failed to verify security parameters: %w", err)