Erratum to "Reweighting NNPDFs: The W lepton asymmetry" [Nucl. Phys. B 849 (1) (2011) 112-143] - Ball, R; Bertone, V; Cerutti, F; Del Debbio, L; Forte, S; Guffanti, A; Latorre, J; Rojo, J; Ubiali, M (2012)