1 Erratum to: Eur. Phys. J. C https://doi.org/10.1140/epjc/s10052-020-7757-5

The Ref. [1] was missing in the published version of the paper [2] and it has to be added to Ref. [3] (Ref. [93] of the original version). The sentence that appears two lines below Eq. (11) of the published version [2] has to be replaced by the following sentence:

The Mellin moments \(\mathcal {\hat{W}}_{ab}^{N_1,N_2}\) are calculated with ANCONT [1, 3], a software library for the analytic continuation of Mellin transforms.