fix(BUX-686): checking nil pointer to nil Metadata

[chris-4chain]

Pull Request Checklist

• 📖 I created my PR using provided : CODE_STANDARDS
• 📖 I have read the short Code of Conduct: CODE_OF_CONDUCT
• 🏠 I tested my changes locally.
• ✅ I have provided tests for my changes.
• 📝 I have used conventional commits.
• 📗 I have updated any related documentation.
• 💾 PR was issued based on the Github or Jira issue.

[github-actions]

Manual Tests

💚 Manual testing by @dorzepowski resulted in success.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 30.00000% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 52.86%. Comparing base (e06f774) to head (177fc64).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #528      +/-   ##
==========================================
- Coverage   52.89%   52.86%   -0.03%     
==========================================
  Files         189      189              
  Lines       10847    10857      +10     
==========================================
+ Hits         5737     5740       +3     
- Misses       4560     4564       +4     
- Partials      550      553       +3     

Flag	Coverage Δ
unittests	52.86% <30.00%> (-0.03%)	⬇️

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

Files	Coverage Δ
engine/datastore/where_builder.go	86.53% <30.00%> (-3.88%)	⬇️

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