Gravar-mail: Crystal structure of catena-poly[[[aqua­bis­(di­methyl­formamide-κO)magnesium(II)]-μ(3)-(2,2′-bi­pyridine-5,5′-di­carboxyl­ato-κ(5) O (2):O (2′):N,N′:O (5))-[di­chlorido­platinum(II)]] di­methyl­formamide monosolvate]