Use QueryHelpers.AddQueryString

Emby.Server.Implementations/HttpServer/HttpListenerHost.cs

@@ -321,7 +321,7 @@ namespace Emby.Server.Implementations.HttpServer
             string pagePathWithoutQueryString = url.Split(new[] { '?' }, StringSplitOptions.RemoveEmptyEntries)[0];
 
             return newQueryString.Count > 0
-                ? $"{pagePathWithoutQueryString}?{string.Join("&", newQueryString.Select(value => value.Key + " = " + string.Join(", ", value.Value)))}"
+                ? QueryHelpers.AddQueryString(pagePathWithoutQueryString, newQueryString.ToDictionary(kv => kv.Key, kv => kv.Value.ToString()))
                 : pagePathWithoutQueryString;
         }