fuzz/asn1parse.c: Clean up non-portable code and catch malloc failure

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15722)

fuzz/asn1parse.c

@@ -23,9 +23,9 @@ static BIO *bio_out;
 
 int FuzzerInitialize(int *argc, char ***argv)
 {
-    bio_out = BIO_new_file("/dev/null", "w");
+    bio_out = BIO_new(BIO_s_null()); /* output will be ignored */
     if (bio_out == NULL)
-        bio_out = BIO_new(BIO_s_mem());
+        return 0;
     OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CRYPTO_STRINGS, NULL);
     ERR_clear_error();
     CRYPTO_free_ex_index(0, -1);