desktop: Fixed digital forms dashboard when duplicate variable codes occur

prs.desktop/Dashboards/Common/DigitalFormsDashboard.xaml.cs

@@ -1425,13 +1425,14 @@ public partial class DigitalFormsDashboard : UserControl,
             {
                 var code = variable.Code.Replace("/", " ");
                 Grid.QuestionCodes[code] = Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(code.ToLower());
-                try
+
+                if (cData.HasColumn(code))
                 {
-                    cData.AddColumn<string>(code);
+                    MessageWindow.ShowError($"Error: duplicate variable code {code}", $"Error: duplicate variable code {code}", title: "Duplicate code");
                 }
-                catch (DuplicateNameException e)
+                else
                 {
-                    MessageWindow.ShowError($"Error: duplicate variable code {code}", e, title: "Duplicate code");
+                    cData.AddColumn<string>(code);
                 }
             }
         }