Fix E_RECOVERABLE_ERROR in category API

category_sort_rows_by_project() is called in 2 steps:

1. with a project id in 1st param to set the "preferred" project (and
   2nd param null)
2. with 2 arrays containing category details

Because of this behavior, the 'array' type hint can't be used on the
first parameter as it throws an error when initializing the sort in
category_get_all_rows().

Regression introduced by 5458f7020999317b35f403fa2a0e477d6182ec12

Fixes 0017515