Dear all,

to simulate a PDE-ODE-System, I was trying to use a compound FE-Space on two different mesh, one with only one DOF (for the ODE). However, it seems that assembling in such a space does not work properly.

Is this a bug or am I using it in an unintended way?

Minimal example:

```
from ngsolve.meshes import Make1DMesh
from ngsolve.meshes import Mesh as NgMesh
from netgen.meshing import *
from ngsolve import *
nx = 10
ngsmesh = Make1DMesh(nx)
ngsmesh_ODE = Make1DMesh(1) # For the ODE, thus only one DOF
fes1 = L2(ngsmesh_ODE, order=0)
fes2 = L2(ngsmesh, order=1, dgjumps=True)
fes = FESpace([fes1,fes2])
u,v = fes.TnT()
m = BilinearForm(fes)
m.components[0] += BFI("mass", coef=1) #u[0]*v[0]*dx
m.components[1] += BFI("mass", coef=1) #u[1]*v[1]*dx
m.Assemble()
print(m.mat)
```