Add error handling in ASN1_i2d_bio.

(Imported from 950d49d43900e67a1f9d02bc1a053a9fdc5c4257.)

Change-Id: Ia41c5076019b8cb16a9af9247b947fba7b20e87a
Reviewed-on: https://boringssl-review.googlesource.com/22725
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

crypto/asn1/a_i2d_fp.c

@@ -81,6 +81,9 @@ int ASN1_i2d_bio(i2d_of_void *i2d, BIO *out, void *x)
     int i, j = 0, n, ret = 1;
 
     n = i2d(x, NULL);
+    if (n <= 0)
+        return 0;
+
     b = (char *)OPENSSL_malloc(n);
     if (b == NULL) {
         OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);