Fix broken change from b3d113e.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8606)

crypto/rand/rand_lib.c

@@ -235,8 +235,9 @@ size_t rand_drbg_get_nonce(RAND_DRBG *drbg,
     struct {
         void * instance;
         int count;
-    } data = { NULL, 0 };
+    } data;
 
+    memset(&data, 0, sizeof(data));
     pool = rand_pool_new(0, min_len, max_len);
     if (pool == NULL)
         return 0;