The icon themes from the main wiki is used on subwikis too

Steps to reproduce

1. on the main wiki, create a page with the following code

   {{velocity}}
   |=transmit|$services.icon.render('transmit')
   {{/velocity}}
   

2. on a subwiki, create a page with the same code
3. on the main wiki, modify IconThemes.Flamingo

   transmit = user
   

4. Save it
5. Go back to your page: a new icon is displayed
6. Go back to the page on the subwiki: the new icon is displayed too.