Validate type of MSG

[lan496]

Fixes: #249

In the example, the orders of FSG and XSG are not consistent due to high mag_symprec.
The PR validates the consistency (by checking a returned construct type from 1 to 4).

[lan496]

@LecrisUT The test with Address sanitizer for LLVM failed, but one for GCC succeeded. I have no idea why this difference happened. Do you have any idea?

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.20 🎉

Comparison is base (06f1799) 85.69% compared to head (b67fcc7) 85.90%.

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Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #267      +/-   ##
===========================================
+ Coverage    85.69%   85.90%   +0.20%     
===========================================
  Files           23       23              
  Lines         6069     6071       +2     
===========================================
+ Hits          5201     5215      +14     
+ Misses         868      856      -12     

Flag	Coverage Δ
c_api	74.23% <100.00%> (+0.52%)	⬆️
fortran_api	37.36% <0.00%> (-0.02%)	⬇️
python_api	82.83% <50.00%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
src/magnetic_spacegroup.c	87.92% <100.00%> (+3.22%)	⬆️

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[LecrisUT]

When possible, can you add some quick comments in the code, e.g. why ASSERT_TRUE(size>0), or why/where it should fail?

[LecrisUT]

LGTM now w.r.t. C coding, but I'll let you guys confirm the technical details of this

[lan496]

@LecrisUT Many thanks! I'll merge this PR after atztogo checks.

[atztogo]

Thanks @lan496 and @LecrisUT!