diff --git a/EnvelopeGenerator.GeneratorAPI/Controllers/EnvelopeController.cs b/EnvelopeGenerator.GeneratorAPI/Controllers/EnvelopeController.cs
index 5cf96857..ce9147a2 100644
--- a/EnvelopeGenerator.GeneratorAPI/Controllers/EnvelopeController.cs
+++ b/EnvelopeGenerator.GeneratorAPI/Controllers/EnvelopeController.cs
@@ -44,7 +44,7 @@ public class EnvelopeController : ControllerBase
         try
         {
             if (User.GetId() is int intId)
-                return await _envelopeService.ReadByUserAsync(intId, min_status: status.Min, max_status: status.Max, ignore_statuses: status.Ignore).ThenAsync(
+                return await _envelopeService.ReadByUserAsync(intId, min_status: status.Min, max_status: status.Max, ignore_statuses: status.Ignore ?? Array.Empty<int>()).ThenAsync(
                     Success: Ok,
                     Fail: IActionResult (msg, ntc) =>
                     {
diff --git a/EnvelopeGenerator.GeneratorAPI/Controllers/HistoryController.cs b/EnvelopeGenerator.GeneratorAPI/Controllers/HistoryController.cs
index 89dcf8ce..ae683738 100644
--- a/EnvelopeGenerator.GeneratorAPI/Controllers/HistoryController.cs
+++ b/EnvelopeGenerator.GeneratorAPI/Controllers/HistoryController.cs
@@ -30,6 +30,10 @@ public class HistoryController : ControllerBase
         _service = service;
     }
 
+    /// <summary>
+    /// Ruft die verfügbaren Referenztypen ab und gibt sie als Schlüssel-Wert-Paare zurück.
+    /// </summary>
+    /// <returns>Ein Ok-Ergebnis mit einem Wörterbuch, das die Referenztypen als Schlüssel-Wert-Paare enthält.</returns>
     [HttpGet("reference-type")]
     [Authorize]
     public IActionResult GetReferenceTypes()