From c7ac4299765c8fbc8adf89f2ec84cb340b6ccd29 Mon Sep 17 00:00:00 2001
From: Jonas Arnold <jonas.arnold@live.de>
Date: Fri, 12 May 2023 21:52:35 +0200
Subject: [PATCH] potentially fixed bug in MultiFormatTextBox which lead to
 application crash

---
 .../MultiFormatTextBox/MultiFormatTextBox.cs                    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MultiTerm.Wpf.CustomControl/MultiFormatTextBox/MultiFormatTextBox.cs b/MultiTerm.Wpf.CustomControl/MultiFormatTextBox/MultiFormatTextBox.cs
index e44b8af..a799c9a 100644
--- a/MultiTerm.Wpf.CustomControl/MultiFormatTextBox/MultiFormatTextBox.cs
+++ b/MultiTerm.Wpf.CustomControl/MultiFormatTextBox/MultiFormatTextBox.cs
@@ -83,7 +83,7 @@ public class MultiFormatTextBox : Control
     ~MultiFormatTextBox()
     {
         // unregister events
-        if (this.CurrentMultiFormatString is INotifyCollectionChanged incc)
+        if (this.CurrentMultiFormatString != null && this.CurrentMultiFormatString is INotifyCollectionChanged incc)
         {
             incc.CollectionChanged -= this.MultiFormatString_CollectionChanged;
         }