Support empty ArraySequence in saving (for empty vtk)

[frheault]

Added a simple check to avoid the np.stack if an array is empty.

The diff looks weird, but it's simply a new if to avoid the coloring part if there is no streamlines

[codecov]

Codecov Report

Merging #593 (fa66ca3) into master (6fe15a6) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #593   +/-   ##
=======================================
  Coverage   87.94%   87.94%           
=======================================
  Files          62       62           
  Lines       13099    13120   +21     
  Branches     1316     1320    +4     
=======================================
+ Hits        11520    11539   +19     
- Misses       1202     1203    +1     
- Partials      377      378    +1     

Impacted Files	Coverage Δ
fury/fury/utils.py	91.47% <0.00%> (-0.28%)	⬇️
fury/fury/tests/test_utils.py	94.74% <0.00%> (+0.13%)	⬆️

[skoudoro]

Hi @frheault,

Thank you for this. We will not add nibabel as a dependency. Unfortunately, you need to change the way you are doing it here.

[skoudoro]

Hi @frheault,

Thank you for the update. Can you look at this last error:

        # Get the 3d points_array
        if not isinstance(lines, list):
>           points_array = lines._data
E           AttributeError: 'numpy.ndarray' object has no attribute '_data'
../fury/utils.py:262: AttributeError
=========================== short test summary info ============================
FAILED ../fury/tests/test_molecular.py::test_bounding_box - AttributeError: '...
========================= 1 failed, 12 passed in 4.03s =========================

[skoudoro]

Hi @frheault,

Can you do this small change and add a small test with different types of empty streamlines.
After, it should be good to go. I might have merged your other PR a bit fast.

Thank you.

ps: since dipy is optional, we will have to use the decorator skipif and optional package for dipy.

[skoudoro]

Thank you for this @frheault, merging