test/crltest.c: Add check for glue2bio

As the glue2bio() could return NULL pointer if fails,
it should be better to check the return value in order
to avoid the use of NULL pointer.
Signed-off-by: NJiasheng Jiang <jiasheng@iscas.ac.cn>
Reviewed-by: NTomas Mraz <tomas@openssl.org>
Reviewed-by: NPaul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17718)

test/crltest.c

@@ -200,9 +200,16 @@ static BIO *glue2bio(const char **pem, char **out)
  */
 static X509_CRL *CRL_from_strings(const char **pem)
 {
+    X509_CRL *crl;
     char *p;
     BIO *b = glue2bio(pem, &p);
-    X509_CRL *crl = PEM_read_bio_X509_CRL(b, NULL, NULL, NULL);
+
+    if (b == NULL) {
+        OPENSSL_free(p);
+        return NULL;
+    }
+
+    crl = PEM_read_bio_X509_CRL(b, NULL, NULL, NULL);
 
     OPENSSL_free(p);
     BIO_free(b);
@@ -214,9 +221,16 @@ static X509_CRL *CRL_from_strings(const char **pem)
  */
 static X509 *X509_from_strings(const char **pem)
 {
+    X509 *x;
     char *p;
     BIO *b = glue2bio(pem, &p);
-    X509 *x = PEM_read_bio_X509(b, NULL, NULL, NULL);
+
+    if (b == NULL) {
+        OPENSSL_free(p);
+        return NULL;
+    }
+
+    x = PEM_read_bio_X509(b, NULL, NULL, NULL);
 
     OPENSSL_free(p);
     BIO_free(b);
@@ -363,6 +377,12 @@ static int test_reuse_crl(void)
     char *p;
     BIO *b = glue2bio(kRevokedCRL, &p);
 
+    if (b == NULL) {
+        OPENSSL_free(p);
+        X509_CRL_free(reused_crl);
+        return 0;
+    }
+
     reused_crl = PEM_read_bio_X509_CRL(b, &reused_crl, NULL, NULL);
 
     OPENSSL_free(p);