Let `dolfinx.fem.forms._zero_form` compile on mixed-domain problems.

[jorgensd]

Summarize the issue

Currently this assumes no entity maps.

How to reproduce the bug

Run the following code

Minimal Example (Python)

from mpi4py import MPI
import numpy as np
import dolfinx
import ufl

mesh = dolfinx.mesh.create_unit_square(MPI.COMM_WORLD, 10, 10)
submesh, entity_map = dolfinx.mesh.create_submesh(
    mesh,
    mesh.topology.dim,
    np.arange(mesh.topology.index_map(mesh.topology.dim).size_local, dtype=np.int32)[
        :-2
    ],
)[:2]

V = dolfinx.fem.functionspace(mesh, ("Lagrange", 1))
Q = dolfinx.fem.functionspace(submesh, ("Lagrange", 1))

u = ufl.TrialFunction(V)
v = ufl.TestFunction(Q)
a = ufl.ZeroBaseForm((u, v))
dolfinx.fem.form(a, entity_maps=[entity_map])

Output (Python)

Traceback (most recent call last):
  File "/root/shared/networks_fenicsx/mwe.py", line 21, in <module>
    dolfinx.fem.form(a, entity_maps=[entity_map])
  File "/root/shared/dolfinx/python/dolfinx/fem/forms.py", line 449, in form
    return _create_form(form)
           ^^^^^^^^^^^^^^^^^^
  File "/root/shared/dolfinx/python/dolfinx/fem/forms.py", line 443, in _create_form
    return _zero_form(form)
           ^^^^^^^^^^^^^^^^
  File "/root/shared/dolfinx/python/dolfinx/fem/forms.py", line 419, in _zero_form
    f = ftype(
        ^^^^^^
RuntimeError: Incompatible mesh. argument entity_maps must be provided.

Version

main branch

DOLFINx git commit

No response

Installation

No response

Additional information

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