Fix in zone_deep_free()

- Was trying to free the hashtable even if there was none.

src/dnslib/zone.c

@@ -609,7 +609,9 @@ void dnslib_zone_deep_free(dnslib_zone_t **zone)
 		return;
 	}
 
-	ck_destroy_table(&(*zone)->table, NULL, 0);
+	if ((*zone)->table != NULL) {
+		ck_destroy_table(&(*zone)->table, NULL, 0);
+	}
 
 	/* has to go through zone twice, rdata may contain references to node
 	   owners earlier in the zone which may be already freed */

src/hash/cuckoo-hash-table.c

@@ -634,6 +634,8 @@ ck_hash_table_t *ck_create_table(uint items)
 void ck_destroy_table(ck_hash_table_t **table, void (*dtor_value)(void *value),
                       int delete_key)
 {
+	assert(table);
+	assert(*table);
 	pthread_mutex_lock(&(*table)->mtx_table);
 
 	// destroy items in tables