fix incorrect check which might break when registering an endpoint class that contains no endpoints

SimpleHttpServer/HttpServer.cs

@@ -87,7 +87,7 @@ public sealed class HttpServer {
     private readonly Dictionary<(string path, string rType), EndpointInvocationInfo> simpleEndpointMethodInfos = new();
     private static readonly Type[] expectedEndpointParameterTypes = new[] { typeof(RequestContext) };
     public void RegisterEndpointsFromType<T>() {
-        if (simpleEndpointMethodInfos.Count == 0)
+        if (stringToTypeParameterConverters.Count == 0)
             RegisterDefaultConverters();
 
         var t = typeof(T);