Set identity flag to false in MatPerm/Butterfly<FPP,Cpu>::toMatSparse.

src/faust_linear_operator/CPU/faust_MatButterfly.hpp

@@ -487,6 +487,7 @@ namespace Faust
 			MatSparse<FPP, Cpu> sp(this->getNbRow(), this->getNbCol());
 			sp.setEyes();
 			multiply(sp, 'N');
+			sp.set_id(false);
 			return sp;
 #else
 			// strange rare bugs occurred with this version (when making a toarray of a pyfaust.Faust containing MatButterfly)

src/faust_linear_operator/CPU/faust_MatPerm.hpp

@@ -456,6 +456,7 @@ namespace Faust
 				tripletList.push_back(Eigen::Triplet<FPP>(i, perm_ids[i], d_ptr[i]));
 			auto sp = MatSparse<FPP, Cpu>(tripletList, s, s);
 			sp.conservativeResize(s, s);
+			sp.set_id(false); //TODO: it might be the identity, verify (add a MatDiag::isDiag(bool verify_id=true), static function)
 			return sp;
 		}