dev: use consts for empty hash

[enitrat]

Time spent on this PR:

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Resolves #1410

What is the new behavior?

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This change is 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.0%. Comparing base (c7896d0) to head (3bf2671).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1431   +/-   ##
=====================================
  Coverage   63.0%   63.0%           
=====================================
  Files         49      49           
  Lines       8332    8332           
=====================================
  Hits        5252    5252           
  Misses      3080    3080           

Flag	Coverage Δ
	63.0% <100.0%> (ø)

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