Replace branched assertions with single assertion to fix compile error

[mborland]

Closes: #144

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.79%. Comparing base (815af30) to head (35a469e).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #145      +/-   ##
===========================================
- Coverage    95.79%   95.79%   -0.01%     
===========================================
  Files          115      115              
  Lines         7642     7640       -2     
===========================================
- Hits          7321     7319       -2     
  Misses         321      321              

Files with missing lines	Coverage Δ
include/boost/random/mersenne_twister.hpp	99.43% <100.00%> (-0.01%)	⬇️

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 815af30...35a469e. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.