Fixed null pointer exception is occured when user created a new page.

lib/models/page-group-relation.js

@@ -143,6 +143,9 @@ class PageGroupRelation {
    */
   static findByPage(page) {
 
+    if (page == null) {
+      return null;
+    }
     return this
       .find({ targetPage: page.id })
       .populate('relatedGroup')

lib/routes/page.js

@@ -342,11 +342,15 @@ module.exports = function(crowi, app) {
     .then(function() {
       return UserGroupRelation.findAllRelationForUser(req.user);
     }).then(function (groupRelations) {
-      renderVars.userRelatedGroups = groupRelations.map(relation => relation.relatedGroup);
+      if (groupRelations != null) {
+        renderVars.userRelatedGroups = groupRelations.map(relation => relation.relatedGroup);
+      }
 
       return PageGroupRelation.findByPage(renderVars.page);
     }).then((pageGroupRelation) => {
-      renderVars.pageRelatedGroup = pageGroupRelation.relatedGroup;
+      if (pageGroupRelation != null) {
+        renderVars.pageRelatedGroup = pageGroupRelation.relatedGroup;
+      }
 
       return Promise.resolve();
     });