potential bug in fem_poisson

[manauref]

In the fem_poisson private header I see this list of LHS kernels

static const lhsstencil_kern_bcx_list_2x ser_lhsstencil_consteps_list_2x[] = {
...
// dirichletx-dirichletx
  { .list = {
...
    // dirichlety-dirichlety
    { .list = {{NULL, NULL, NULL, NULL},
               {fem_poisson_lhs_stencil_consteps_2x_ser_p1_inx_periodicx_iny_periodicy,
                fem_poisson_lhs_stencil_consteps_2x_ser_p1_lox_dirichletx_iny_periodicy,
                fem_poisson_lhs_stencil_consteps_2x_ser_p1_upx_dirichletx_iny_periodicy,
                fem_poisson_lhs_stencil_consteps_2x_ser_p1_inx_periodicx_loy_dirichlety,
                fem_poisson_lhs_stencil_consteps_2x_ser_p1_inx_periodicx_upy_dirichlety,
                fem_poisson_lhs_stencil_consteps_2x_ser_p1_lox_dirichletx_loy_dirichlety,
                fem_poisson_lhs_stencil_consteps_2x_ser_p1_lox_dirichletx_upy_dirichlety,
                fem_poisson_lhs_stencil_consteps_2x_ser_p1_upx_dirichletx_loy_dirichlety,
                fem_poisson_lhs_stencil_consteps_2x_ser_p1_upx_dirichletx_upy_dirichlety},

as the comments indicate, these kernels should be the dirichletx-dirichletx-dirichlety-dirichlety kernels, but there's some periodic x and periodic y kernels in there. Seems suspicious.