Now disposes the event handler if a cancellation token is triggered while waiting for the HandleCreated event

Author: SteffenSH

Serilog.Sinks.RichTextBox.WinForms.Colored/Sinks/RichTextBoxForms/Extensions/RichTextBoxExtensions.cs

@@ -63,9 +63,15 @@ public static void SetRtf(this RichTextBox richTextBox, string rtf, bool autoScr
                 var mre = new ManualResetEventSlim();
                 EventHandler eh = (sender, args) => mre.Set();
                 richTextBox.HandleCreated += eh;
-                if (richTextBox.IsHandleCreated) mre.Set();
-                mre.Wait(token);
-                richTextBox.HandleCreated -= eh;
+                if (richTextBox.IsHandleCreated) mre.Set();
+                try
+                {
+                    mre.Wait(token);
+                }
+                finally
+                {
+                    richTextBox.HandleCreated -= eh;
+                }
             }
 
             if (richTextBox.InvokeRequired)