fix: MainPage.ets, 国殇代码容错处理

@@ -44,6 +44,7 @@ struct MainPage {
     })
 
     let dataModelStr : string = SPHelper.default.getSync(SpConstants.APP_LAUNCH_PAGE_DATA_MODEL,'') as string
+    if (dataModelStr) {
       let dataModel : LaunchDataModel = JSON.parse(dataModelStr)
       console.log(dataModelStr)
       // 处理国殇模式数据
@@ -52,6 +53,7 @@ struct MainPage {
       GrayManage.setMourning(mourns)
       AppStorage.setOrCreate('GrayManage', GrayManage)
     }
+  }
 
   pageTransition() {
     PageTransitionEnter({ type: RouteType.None, duration: 0 })