I added sentinel error values for jobs not being found and no jobs being updated by the `CreateTaskForRunner` function. This avoids the nilnil antipattern and allows the nilnil lint to be enabled for the `models/actions/task.go` file again.
The handling of these new errors was added to the `PickTask` function in `services/actions/task.go`.
Related issue: https://codeberg.org/forgejo/forgejo/issues/11261
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12768
Reviewed-by: limiting-factor <limiting-factor@noreply.codeberg.org>
Reviewed-by: elle <0xllx0@noreply.codeberg.org>
