Unittest fail with regularisation toolkit 25.0.0

[paskino]

Description

I bumped the CCPi-Regularisation toolkit version from 24.1.0 in the GHA to 25.0.0 and the unittest fail.

[11](https://github.com/TomographicImaging/CIL/actions/runs/21873769273/job/63136513662?pr=2287#step:6:512)
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ERROR: test_TotalVariation_vs_FGP_TV_gpu (test_PluginsRegularisation.TestPlugin.test_TotalVariation_vs_FGP_TV_gpu)
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Traceback (most recent call last):
  File "/home/runner01/_work/CIL/CIL/Wrappers/Python/test/test_PluginsRegularisation.py", line 293, in test_TotalVariation_vs_FGP_TV_gpu
    res_TV_regtoolkit_gpu_iso = TV_regtoolkit_gpu_iso.proximal(self.data, tau=1.0)
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/runner/runner01/miniconda/envs/CIL-21873769273.2739/lib/python3.11/site-packages/cil/plugins/ccpi_regularisation/functions/regularisers.py", line 77, in proximal
    res, info = self.proximal_numpy(arr, tau)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/runner/runner01/miniconda/envs/CIL-21873769273.2739/lib/python3.11/site-packages/cil/plugins/ccpi_regularisation/functions/regularisers.py", line 260, in proximal_numpy
    solution = self._fista_on_dual_rof(in_arr, tau)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/runner/runner01/miniconda/envs/CIL-21873769273.2739/lib/python3.11/site-packages/cil/plugins/ccpi_regularisation/functions/regularisers.py", line 240, in _fista_on_dual_rof
    res = regularisers.FGP_TV(\
          ^^^^^^^^^^^^^^^^^^^^^
  File "/opt/runner/runner01/miniconda/envs/CIL-21873769273.2739/lib/python3.11/site-packages/ccpi/filters/regularisers.py", line 25, in wrapper
    return GPU_func(*args, gpu_device=0 if device == 'gpu' else device, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'NoneType' object is not callable

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Ran 266 tests in 78.650s

Environment

import cil, sys
print(cil.version.version, cil.version.commit_hash, sys.version, sys.platform)