don't crash on badly formatted error messages

src/BreCalClient/MainWindow.xaml.cs

@@ -1066,6 +1066,8 @@ namespace BreCalClient
             // type=8, created=datetime.datetime(2024, 8, 28, 15, 13, 14), modified=None) with Flags: 42\"}
             Match m = Regex.Match(message, "\\{(.*)\\}");
             if ((m != null) && m.Success)
+            {
+                try
                 {
                     dynamic? msg = JsonConvert.DeserializeObject(m.Value);
                     if (msg != null)
@@ -1073,6 +1075,8 @@ namespace BreCalClient
                         message = msg.message;
                     }
                 }
+                catch (Exception) { }
+            }                
 
             _log.ErrorFormat("{0} - {1}", caption, message);