Fix segfault when computing the expected value vector

[robomics]

Address segfault that could occur when computing the expected value vector density for chromosomes whose size is smaller than the bin size.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 84.85%. Comparing base (08d5109) to head (e433ad9).

Files	Patch %	Lines
...ude/hictk/impl/expected_values_aggregator_impl.hpp	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #147      +/-   ##
==========================================
- Coverage   84.86%   84.85%   -0.01%     
==========================================
  Files         117      117              
  Lines       10022    10024       +2     
==========================================
+ Hits         8505     8506       +1     
- Misses       1517     1518       +1     

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