From 5f6df6bce95d4bc553e85a17409c42452f5eba81 Mon Sep 17 00:00:00 2001
From: Rene Evertz <rene.evertz@ownsoft.de>
Date: Wed, 26 Nov 2025 15:37:51 +0100
Subject: [PATCH] Validator erweitert

---
 Shared/Core/GkvValidator.cs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Shared/Core/GkvValidator.cs b/Shared/Core/GkvValidator.cs
index 71d09dd21..64856cdec 100644
--- a/Shared/Core/GkvValidator.cs
+++ b/Shared/Core/GkvValidator.cs
@@ -202,6 +202,9 @@ namespace BS.Shared.Core
         }
 		public static bool IsInvoiceNumberValid(string invoiceNumber)
 		{
+            if (string.IsNullOrEmpty(invoiceNumber))
+                return false;
+
 			var pattern = @"^(?!.*[-/]{2})(?![-/])(?!.*[-/]$)[A-Za-z0-9]+(?:[/-][A-Za-z0-9]+)*$";
 
             return Regex.IsMatch(invoiceNumber, pattern);