Fix: avoid error caused by broken data

lib/routes/page.js

@@ -73,10 +73,11 @@ module.exports = function(crowi, app) {
     }
 
     Revision.findRevisionList(pageData.path, {}, function(err, tree) {
+      var revision = pageData.revision || {};
       res.render(req.query.presentation ? 'page_presentation' : 'page', {
         path: pageData.path,
-        revision: pageData.revision || {},
-        author: pageData.revision.author || false,
+        revision: revision,
+        author: revision.author || false,
         page: pageData,
         tree: tree || [],
       });