Not affiliated trying to access to q=gradebook/

Hi:
I am trying to take a look to the last changes but I think I found a bug.

When I try to access to ?q=gradebook/ I get a "You are not yet affiliated with a gradebook." but if I tried to access directly (I mean ?q=gradebook/64) it works. I have been looking into the code and I think there is a problem with gradebookapi_gradebook_load call into gradebook_list_page function. I'ts have been called with a correct tid (64 in my case) but it returns nothing.