fix blob_client_list

Author: NazariiDenha

rollup/da_syncer/blob_client/blob_client_list.go

@@ -30,7 +30,7 @@ func (c *BlobClientList) GetBlobByVersionedHash(ctx context.Context, versionedHa
 
 	for i := 0; i < len(c.list); i++ {
 		blob, err := c.list[c.nextPos()].GetBlobByVersionedHash(ctx, versionedHash)
-		if err != nil {
+		if err == nil {
 			return blob, nil
 		}
 

rollup/da_syncer/da/commitV1.go

@@ -59,6 +59,9 @@ func NewCommitBatchDAV1WithBlobDecodeFunc(ctx context.Context, db ethdb.Database
 	if err != nil {
 		return nil, fmt.Errorf("failed to fetch blob from blob client, err: %w", err)
 	}
+	if blob == nil {
+		return nil, fmt.Errorf("unexpected, blob == nil and err != nil, batch index: %d, versionedHash: %s, blobClient: %T", batchIndex, versionedHash.String(), blobClient)
+	}
 
 	// compute blob versioned hash and compare with one from tx
 	c, err := kzg4844.BlobToCommitment(blob)