Fix build

Author: crobibero

Jellyfin.Plugin.Webhook/Helpers/HandlebarsFunctionHelpers.cs

@@ -1,8 +1,8 @@
 using System;
 using System.Globalization;
-using System.Text.Json.JsonEncodedText;
 using System.Web;
 using HandlebarsDotNet;
+using System.Text.Json;
 
 namespace Jellyfin.Plugin.Webhook.Helpers;
 
@@ -60,13 +60,16 @@ public static class HandlebarsFunctionHelpers
         writer.WriteSafeString(encodedValue);
     };
 
-    private static readonly HandlebarsHelper JsonEncodeHelper = (writer, context, parameters) => {
+    private static readonly HandlebarsHelper JsonEncodeHelper = (writer, context, parameters) =>
+    {
         if (parameters.Length != 1)
         {
             throw new HandlebarsException("{{json_encode}} helper must have exactly one argument");
         }
 
         var valueToEncode = GetStringValue(parameters[0]);
+        ArgumentNullException.ThrowIfNull(valueToEncode);
+
         var encodedValue = JsonEncodedText.Encode(valueToEncode).ToString();
         writer.WriteSafeString(encodedValue);
     };