Failure to run the simulation_zone example on blender 4.0 (and 3.6)

Hello,
I'm starting from the default cube on which I add a geometry node modifier,
I then type the following script (from the documentation) in the built-in editor :

from geometry_script import *

@tree
def test_sim(geometry: Geometry):
@simulation_zone
def my_sim(delta_time, geometry: Geometry, value: Float):
return (False, geometry, value)
return my_sim(geometry, 0.26).value

I get the following error message :

Python: Traceback (most recent call last):
File "\Text", line 4, in
File "C:\Users\tsatse\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\geometry-script-main\api\tree.py", line 149, in tree
return build_tree(name)
File "C:\Users\tsatse\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\geometry-script-main\api\tree.py", line 113, in build_tree
outputs = builder(**builder_inputs)
File "\Text", line 8, in test_sim
File "C:\Users\tsatse\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\geometry-script-main\api\static\simulation.py", line 21, in wrapped
simulation_in = State.current_node_tree.nodes.new(bpy.types.GeometryNodeSimulationInput.__name__)
AttributeError: 'NoneType' object has no attribute 'nodes'

(my OS is windows 10)