Make find many operations return empty slice instead of nil

[sunboyy]

Previously, find many operations return nil when there is no data that matches the query. This leads to null when the result is encoded into other formats like JSON, which is inconsistent. This MR fixes that by returning an empty slice instead of nil value.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (97619d4) 97.39% compared to head (b736b94) 97.39%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #40   +/-   ##
=======================================
  Coverage   97.39%   97.39%           
=======================================
  Files          27       27           
  Lines        1341     1345    +4     
=======================================
+ Hits         1306     1310    +4     
  Misses         20       20           
  Partials       15       15           

Flag	Coverage Δ
unittests	97.39% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

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