fix checking permission in API to delete share link

packages/app/src/server/routes/apiv3/share-links.js

@@ -249,21 +249,25 @@ module.exports = (crowi) => {
   */
   router.delete('/:id', loginRequired, csrf, validator.deleteShareLink, apiV3FormValidator, async(req, res) => {
     const { id } = req.params;
+    const { user } = req;
 
     try {
-      const deletedShareLink = await ShareLink.findOne({ _id: id });
+      const shareLinkToDelete = await ShareLink.findOne({ _id: id });
 
       // check permission
-      const page = await Page.findByIdAndViewer(deletedShareLink.relatedPage, req.user);
-      if (page == null) {
-        const msg = 'Page is not found or forbidden';
-        logger.error('Error', msg);
-        return res.apiv3Err(new ErrorV3(msg, 'delete-shareLink-failed'));
+      if (!user.isAdmin) {
+        const page = await Page.findByIdAndViewer(shareLinkToDelete.relatedPage, user);
+        const isPageExists = (await Page.count({ _id: shareLinkToDelete.relatedPage }) > 0);
+        if (page == null && isPageExists) {
+          const msg = 'Page is not found or forbidden';
+          logger.error('Error', msg);
+          return res.apiv3Err(new ErrorV3(msg, 'delete-shareLink-failed'));
+        }
       }
 
       // remove
-      await deletedShareLink.remove();
-      return res.apiv3({ deletedShareLink });
+      await shareLinkToDelete.remove();
+      return res.apiv3({ deletedShareLink: shareLinkToDelete });
     }
     catch (err) {
       const msg = 'Error occurred in delete share link';