Thanks. I did as you suggested, first adding a new style but got the same error. Then i edited the config.php and now its working.
Any idea of how i can narrow it down to find out which of the mods is making this error?
Remove that line you added to config.php and then disable your modifications one-by-one testing this issue each time in-between. When you disable a mod and the issue disappears, you know which one is causing the problem.