fix: handle empty inputs in `CircleSort`

[vil02]

This PR adds tests for CircleSort and fixes the infinite loop occurring for empty input.

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized it.
• [x] All filenames are in PascalCase.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [x] All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 37.55%. Comparing base (6bde5d7) to head (9a7a5e5).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5121      +/-   ##
============================================
+ Coverage     37.36%   37.55%   +0.18%     
- Complexity     2350     2364      +14     
============================================
  Files           517      517              
  Lines         15613    15605       -8     
  Branches       2968     2965       -3     
============================================
+ Hits           5834     5860      +26     
+ Misses         9491     9458      -33     
+ Partials        288      287       -1     

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