Rearrange ASN1_STRING_copy slightly.

Not especially important, but leaving the input unchanged on malloc
failure is a little tidier.

Change-Id: Ia001260edcc8d75865d0d75ac0fe596205f83c48
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/44048
Reviewed-by: Adam Langley <agl@google.com>

crypto/asn1/asn1_lib.c

diff --git a/crypto/asn1/asn1_lib.c b/crypto/asn1/asn1_lib.c
index 5fdbd5b..06fd9d7 100644
--- a/crypto/asn1/asn1_lib.c
+++ b/crypto/asn1/asn1_lib.c
@@ -313,9 +313,9 @@
 {
     if (str == NULL)
         return 0;
-    dst->type = str->type;
     if (!ASN1_STRING_set(dst, str->data, str->length))
         return 0;
+    dst->type = str->type;
     dst->flags = str->flags;
     return 1;
 }