crypto/x509: return err if marshalPublicKey fails to marshal an rsa public key

Change-Id: I9bd5c1b66fd90f0b54bd1a8f3e57b6830d2b7733
Reviewed-on: https://go-review.googlesource.com/13846Reviewed-by: Adam Langley <agl@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/crypto/x509/x509.go

@@ -56,6 +56,9 @@ func marshalPublicKey(pub interface{}) (publicKeyBytes []byte, publicKeyAlgorith
 			N: pub.N,
 			E: pub.E,
 		})
+		if err != nil {
+			return nil, pkix.AlgorithmIdentifier{}, err
+		}
 		publicKeyAlgorithm.Algorithm = oidPublicKeyRSA
 		// This is a NULL parameters value which is technically
 		// superfluous, but most other code includes it and, by