Mentions notifications are only received on pages watched by the user

Mentions notifications are only received if the mentions is made on a page watched by a user, or if the user doesn't have any filters.

Reproduction steps:

• Register a new user and login with it
• Create a new page
• Check that Mention notification alert are enabled and an inclusive filter has been created for the page you created (default behaviour)
• Logout and login with admin
• Create new comment in Main.WebHome with a mention to the user you created first and do the same on the page the user created
• Logout and login again with the first user and check notifications

Expected result:

• The user should receive 3 notifications: 2 for the 2 mentions, and 1 for the comment on the page created

Obtained result:

• 2 notifications are received: 1 for the comment made on the page created, and 1 for the mention made on the same page
• the mention made on Main.WebHome is never notified