Check that coarse is non zero
Check that coarse is non zero

ddemidov/amgcl,ddemidov/amgcl,huahbo/amgcl,ddemidov/amgcl,dondieselkopf/amgcl,huahbo/amgcl,dondieselkopf/amgcl,dondieselkopf/amgcl,ddemidov/amgcl,huahbo/amgcl