Gravar-mail: Bis(methanol-1κO)tetra-μ-pyridazine-1:2κ(4) N:N′;2:3κ(4) N:N′-di-μ-thio­cyanato-1:2κ(2) N:N;2:3κ(2) N:N-tetrathio­cyanato-1κ(2) N,3κ(2) N-trinickel(II) methanol tetra­solvate