In notification emails, the tree of modified pages is sometimes not rendered properly

I'd recommend to hook up XWiki to a fake email server such as MailHog (https://github.com/mailhog/MailHog) for reproducing this issue.

Steps to reproduce :

• On a clean instance, open one session with the default XWiki "Admin" account and create another user, named "TestUser" in my case.
• Update the notification preferences of the Admin user so that he watches every document modification in the wiki, and gets daily notification emails about these modifications
• With the Admin user, create two pages "Space1" and "Space2"
• With the test user, create two pages named "My page" within "Space1" and "Space2". The final tree of the wiki should look like that :

• Now go in Scheduler.WebHome, and trigger the Notification daily email sender job
• Observe the email that the admin got :

Expected : the email displays a tree including only pages that were modified in the wiki
Actual : we don't see the parent pages of the two pages that were created, and thus, the user isn't able to distinguish which page comes from which space.

I'm reporting this as a bug (and not as a new feature) as when a page and one of its children are modified, they are rendered as a tree, see for example the screenshot below, resulting in the modification of the pages Space1.WebHome and Space1.My page.WebHome.