Don't write out a bad OID

If we don't have OID data for an object then we should fail if we
are asked to encode the ASN.1 for that OID.

(Imported from upstream's f3f8e72f494b36d05e0d04fe418f92b692fbb261.)

Change-Id: I3c3d3a3b236bca374fde3c0d02504140f2992602
Reviewed-on: https://boringssl-review.googlesource.com/27065
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

crypto/asn1/tasn_enc.c

@@ -583,6 +583,8 @@ int asn1_ex_i2c(ASN1_VALUE **pval, unsigned char *cout, int *putype,
         otmp = (ASN1_OBJECT *)*pval;
         cont = otmp->data;
         len = otmp->length;
+        if (cont == NULL || len == 0)
+            return -1;
         break;
 
     case V_ASN1_NULL: