make ratelimit section optional (#168)

arch/src/ratelimit.rs

@@ -404,6 +404,14 @@ mod test {
     use std::num::NonZero;
     use std::thread;
 
+    #[test]
+    fn make_ratelimits_optional() {
+        let ratelimits_config = Vec::new();
+
+        // Initialize in the main thread.
+        ratelimits(Some(ratelimits_config));
+    }
+
     #[test]
     fn different_threads_have_same_ratelimit_data_structure() {
         let ratelimits_config = Some(vec![Ratelimit {