Case T-679/16: Judgment of the General Court of 26 February 2019 — Athletic Club v Commission (State aid — Aid granted by the Spanish authorities to certain professional football clubs — Preferential tax rate on the income of the clubs authorised to operate as non-profit organisations — Decision declaring that the aid is incompatible with the internal market — Action for annulment — Interest in bringing proceedings — Admissibility — Infra-State measure — Selective nature — Distortion of competition — Effect on trade between Member States — Alteration to existing aid — Duty to state reasons)