test for peak_slicer() cannot pass

If you run pytest -svv fury/tests/test_actors.py::test_peak_slicer you will see:
fury/tests/test_actors.py::test_peak_slicer FAILED

========================================================================== FAILURES ========================================================================== 
______________________________________________________________________ test_peak_slicer ______________________________________________________________________ 

interactive = False

    def test_peak_slicer(interactive=False):
        _peak_dirs = np.array([[1, 0, 0], [0, 1, 0], [0, 0, 1]], dtype='f4')
        # peak_dirs.shape = (1, 1, 1) + peak_dirs.shape

        peak_dirs = np.zeros((11, 11, 11, 3, 3))

        peak_values = np.random.rand(11, 11, 11, 3)

        peak_dirs[:, :, :] = _peak_dirs

        scene = window.Scene()
>       peak_actor = actor.peak_slicer(peak_dirs)

fury\tests\test_actors.py:613:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  
fury\actor.py:1538: in peak_slicer
    peak_actor.display_extent(
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  

self = <PeakSlicerActor(0x000001E5B17CECF0) at 0x000001E5B7291780>, x1 = 0, x2 = 10, y1 = 0, y2 = 10, z1 = 5, z2 = 5

    def display_extent(self, x1, x2, y1, y2, z1, z2):

        tmp_mask = np.zeros(grid_shape, dtype=bool)
        tmp_mask[x1 : x2 + 1, y1 : y2 + 1, z1 : z2 + 1] = True
        tmp_mask = np.bitwise_and(tmp_mask, mask)

        ijk = np.ascontiguousarray(np.array(np.nonzero(tmp_mask)).T)
        if len(ijk) == 0:
            self.SetMapper(None)
            return
        if affine is not None:
            ijk_trans = np.ascontiguousarray(apply_affine(affine, ijk))
        list_dirs = []
        for index, center in enumerate(ijk):
            # center = tuple(center)
            if affine is None:
                xyz = center[:, None]
            else:
                xyz = ijk_trans[index][:, None]
            xyz = xyz.T
            for i in range(peaks_dirs[tuple(center)].shape[-2]):

                if peaks_values is not None:
                    pv = peaks_values[tuple(center)][i]
                else:
                    pv = 1.0
                if symmetric:
                    dirs = np.vstack(
                        (
                            -peaks_dirs[tuple(center)][i] * pv + xyz,
                            peaks_dirs[tuple(center)][i] * pv + xyz,
                        )
                    )
                else:
                    dirs = np.vstack((xyz, peaks_dirs[tuple(center)][i] * pv + xyz))
                list_dirs.append(dirs)
>       colors = check_color_ndarray(colors)
E       UnboundLocalError: cannot access local variable 'colors' where it is not associated with a value

fury\actor.py:1503: UnboundLocalError
================================================================== short test summary info =================================================================== 
FAILED fury/tests/test_actors.py::test_peak_slicer - UnboundLocalError: cannot access local variable 'colors' where it is not associated with a value
===================================================================== 1 failed in 1.40s ======================================================================
I will investigate it when I finish the current PR. If anyone has the clue, please share:)
fury-gl / fury

test for peak_slicer() cannot pass #772
