[Bug-gnuzilla] Customize mode source code?

[cptvlaze]

Good afternoon:

I'm trying to access to IceCat source code in order to fix a little error: when you enter to the 'Customize' menu (the one where you can edit the position of your toolbars & stuff), you can find a 'Themes' section in the lower left part of the screen. If you click it, and then click on "Get More Themes", IceCat will bring you to a 'broken' link, which returns an error.

I want to change that link to the official Firefox theme repository, but I can't find where it is stored.

Any clues? Thank you.