Favorites should not consider unread children

If a favorite is made on a folder containing childrens, this favorite should only be bold when there are unread message in it, not when the original folder has children with unreads.

Steps to reproduce

• choose a folder with children and add it to favorites
• the favorite shows the unread messages of the original folder
• add more unreads also to the children folders
• now view all the favorite folder's messages or mark them as seen

Expected behaviour

• the favorite is no more bold, while the original folder is bold

Actual behaviour

• the favorite keeps bold, as the original folder