Updated default value

PixiEditor/ViewModels/SubViewModels/Main/UpdateViewModel.cs

@@ -86,7 +86,7 @@ namespace PixiEditor.ViewModels.SubViewModels.Main
 
         private async void Owner_OnStartupEvent(object sender, EventArgs e)
         {
-            if (PreferencesSettings.GetPreference<bool>("CheckUpdatesOnStartup"))
+            if (PreferencesSettings.GetPreference<bool>("CheckUpdatesOnStartup", true))
             {
                 await CheckForUpdate();
             }