message: Verify integrators are used correctly.
diff: @@ -119,6 +119,8 @@ public:
  {
  Ceed ceed(internal::ceed);
  mfem::Mesh &mesh = *fes.GetMesh();
  + MFEM_VERIFY(!(!indices && mesh.GetNumGeometries(mesh.Dimension()) > 1),
  + "Use ceed::MixedIntegrator on mixed meshes.");
  InitCoefficient(Q, mesh, irm, nelem, indices, coeff, info.ctx);
  bool const_coeff = coeff->IsConstant();
  std::string build_func = const_coeff ? info.build_func_const
  @@ -383,6 +385,8 @@ public:
  {
  Ceed ceed(internal::ceed);
  Mesh &mesh = *fes.GetMesh();
  + MFEM_VERIFY(!(!indices && mesh.GetNumGeometries(mesh.Dimension()) > 1),
  + "Use ceed::MixedIntegrator on mixed meshes.");
  InitCoefficient(Q, mesh, irm, nelem, indices, coeff, info.ctx);
  bool const_coeff = coeff->IsConstant();
  std::string apply_func = const_coeff ? info.apply_func_mf_const
  