fix(python): Default to None in pycapsule interface export

[kylebarron]

Closes #17921

[WillAyd]

Awesome thanks @kylebarron for the quick turnaround

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.50%. Comparing base (5fc791c) to head (6d13cca).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17922      +/-   ##
==========================================
+ Coverage   80.49%   80.50%   +0.01%     
==========================================
  Files        1493     1493              
  Lines      196477   196477              
  Branches     2813     2813              
==========================================
+ Hits       158155   158180      +25     
+ Misses      37801    37776      -25     
  Partials      521      521              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[ritchie46]

Thanks for the report @WillAyd, and thank you @kylebarron for the quick fix.