more robust error handling on Whitelist

src/main/java/eu/mhsl/craftattack/spawn/appliances/whitelist/Whitelist.java

@@ -95,6 +95,8 @@ public class Whitelist extends Appliance {
                 uuid
             );
 
+        if(response.status() != HttpStatus.OK) throw new IllegalStateException(String.format("Http Reponse %d", response.status()));
+
         return response.data();
     }