Default DesktopApp to the standard UI state

src/desktop/mod.rs

@@ -110,7 +110,7 @@ impl DesktopAppState for DesktopUiState {
     }
 }
 
-pub struct DesktopApp<State: DesktopAppState> {
+pub struct DesktopApp<State: DesktopAppState = DesktopUiState> {
     rsc: StdRsc<State>,
     state: State,
     task_recv: TaskMsgReceiver<StdRsc<State>>,