make it compatible to older versions that didn't need boundary_indices in build_matrices

git-svn-id: https://svn.dealii.org/trunk@20507 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/deal.II/include/multigrid/mg_transfer.h b/deal.II/deal.II/include/multigrid/mg_transfer.h
index 0a7e9b618c49425f0d6c79cf957917a687136b2a..61ad98b3d5a48f91b1138a75fff8c865a34e25c6 100644 (file)
--- a/deal.II/deal.II/include/multigrid/mg_transfer.h
+++ b/deal.II/deal.II/include/multigrid/mg_transfer.h
@@ -88,6 +88,7 @@ class MGTransferPrebuilt : public MGTransferBase<VECTOR>
     template <int dim, int spacedim>
     void build_matrices (const MGDoFHandler<dim,spacedim> &mg_dof,
     const std::vector<std::set<unsigned int> >&boundary_indices
+                        = std::vector<std::set<unsigned int> >()
         );
 
     virtual void prolongate (const unsigned int    to_level,