QuadFormAndIsom: add a missing check and remove some unnecessary @req

[StevellM]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.60%. Comparing base (4ab6f4d) to head (5f77a8f).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4262      +/-   ##
==========================================
- Coverage   84.60%   84.60%   -0.01%     
==========================================
  Files         640      640              
  Lines       85117    85118       +1     
==========================================
- Hits        72011    72010       -1     
- Misses      13106    13108       +2     

Files with missing lines	Coverage Δ
experimental/QuadFormAndIsom/src/embeddings.jl	96.62% <100.00%> (ø)
experimental/QuadFormAndIsom/src/enumeration.jl	93.68% <100.00%> (+0.01%)	⬆️
experimental/QuadFormAndIsom/test/runtests.jl	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

[afkafkafk13]

Thank you! All checks are still there, but the change now allows to properly handle return values without catching thrown errors.