The magnetic response of CaK(Fe0.949Ni0.051)(4)As-4 was investigated by means of the muon spin rotation/relaxation. The long-range commensurate magnetic order sets in below the Neel temperature T-N = 50.0(5) K. The density-functional theory calculations have identified three possible muon stopping sites. The experimental data were found to be consistent with only one type of magnetic structure, namely, the long-range magnetic spin-vortex-crystal order with the hedgehog motif within the ab plane and the antiferromagnetic stacking along the c direction. The value of the ordered magnetic moment at T approximate to 3 K was estimated to be m(Fe) = 0.38(11)mu(B) (mu(B) is the Bohr magneton). A microscopic coexistence of magnetic and superconducting phases accompanied by a reduction of the magnetic order parameter below the superconducting transition temperature T-c similar or equal to 9 K is observed. Comparison with 11, 122, and 1144 families of Fe-based pnictides points to existence of correlation between the reduction of the magnetic order parameter at T -> 0 and the ratio of the transition temperatures T-c/T-N. Such correlations were found to be described by Machida's model for coexistence of itinerant spin-density-wave magnetism and superconductivity [K. Machida, T. Phys. Soc. Jpn. 50, 2195 (1981); S. L. Bud'ko et al., Phys. Rev. B 98, 144520 (2018)].