Check pointer to magnetic dataset before free

[lan496]

Fixes #348

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (bf0b4b7) 83.55% compared to head (cc63cb3) 83.68%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #349      +/-   ##
===========================================
+ Coverage    83.55%   83.68%   +0.12%     
===========================================
  Files           24       24              
  Lines         8154     8144      -10     
===========================================
+ Hits          6813     6815       +2     
+ Misses        1341     1329      -12     

Flag	Coverage Δ
c_api	76.45% <100.00%> (+0.02%)	⬆️
fortran_api	56.29% <0.00%> (ø)
python_api	80.54% <0.00%> (+0.12%)	⬆️
unit_tests	1.24% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/spglib.c	72.48% <100.00%> (+0.16%)	⬆️

... and 1 file with indirect coverage changes

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