add population for pages about group

src/server/routes/apiv3/user-group.js

@@ -587,6 +587,10 @@ module.exports = (crowi) => {
         populate: {
           path: 'lastUpdateUser',
           select: User.USER_PUBLIC_FIELDS,
+          populate: {
+            path: 'imageAttachment',
+            select: User.IMAGE_POPULATION,
+          },
         },
       });