Handle empty input in median

[vil02]

Pull Request Template

Description

The median function crashes for empty inputs. Since there is no nan for types integer types, I decided to return Option<T> from median.

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected) (well, I change the return type, but everything works).

Checklist:

• I ran bellow commands using the latest version of rust nightly.
• I ran cargo clippy --all -- -D warnings just before my last commit and fixed any issue that was found.
• I ran cargo fmt just before my last commit.
• I ran cargo test just before my last commit and all tests passed.
• I checked COUNTRIBUTING.md and my code follows its guidelines.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ed80173) 94.40% compared to head (a9f6ce3) 94.40%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #612   +/-   ##
=======================================
  Coverage   94.40%   94.40%           
=======================================
  Files         269      269           
  Lines       21850    21855    +5     
=======================================
+ Hits        20628    20633    +5     
  Misses       1222     1222           

Files	Coverage Δ
src/math/average.rs	100.00% <100.00%> (ø)

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

[siriak]

Looks good, thanks!