Fix memory leak in BIO_free if there is no destroy function.

Based on an original patch by Neitrino Photonov <neitrinoph@gmail.com>

PR#3439

crypto/bio/bio_lib.c

@@ -132,8 +132,8 @@ int BIO_free(BIO *a)
 
 	CRYPTO_free_ex_data(CRYPTO_EX_INDEX_BIO, a, &a->ex_data);
 
-	if ((a->method == NULL) || (a->method->destroy == NULL)) return(1);
-	a->method->destroy(a);
+	if ((a->method != NULL) && (a->method->destroy != NULL))
+		a->method->destroy(a);
 	OPENSSL_free(a);
 	return(1);
 	}