WIP: Fix Make functions use null as a way to delete value

[Aviortheking]

Fixes #23

[codecov]

Codecov Report

Merging #24 (c45351d) into master (7ce7daf) will decrease coverage by 2.34%.
The diff coverage is 82.60%.

❗ Current head c45351d differs from pull request most recent head 580da76. Consider uploading reports for the commit 580da76 to get more accurate results

@@            Coverage Diff             @@
##           master      #24      +/-   ##
==========================================
- Coverage   95.41%   93.06%   -2.35%     
==========================================
  Files           3        3              
  Lines         327      303      -24     
  Branches       87       87              
==========================================
- Hits          312      282      -30     
- Misses         15       21       +6     

Impacted Files	Coverage Δ
packages/url-manager/src/URLManager.ts	91.62% <82.60%> (-2.96%)	⬇️
packages/easy-sitemap/src/Sitemap.ts	87.75% <0.00%> (-0.49%)	⬇️
packages/object-util/src/ObjectUtil.ts	100.00% <0.00%> (ø)

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[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

76.3% Coverage
0.0% Duplication