do not show alert if no downloadurl

src/provider.tsx

@@ -124,20 +124,20 @@ export const PushyProvider = ({
     setUpdateInfo(info);
     if (info.expired) {
       const { downloadUrl } = info;
+      if (downloadUrl) {
         showAlert('提示', '您的应用版本已更新，点击更新下载安装新版本', [
           {
             text: '更新',
             onPress: () => {
-            if (downloadUrl) {
               if (Platform.OS === 'android' && downloadUrl.endsWith('.apk')) {
                 downloadAndInstallApk(downloadUrl);
               } else {
                 Linking.openURL(downloadUrl);
               }
-            }
             },
           },
         ]);
+      }
     } else if (info.update) {
       showAlert(
         '提示',