fix(event cache store): shortcut when there's no duplicate events to check at all

[bnjbvr]

Otherwise this causes a panic when repeating the events variable, when generating the SQL query below.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.77%. Comparing base (31e78c2) to head (e4d6ebe).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4665      +/-   ##
==========================================
- Coverage   85.78%   85.77%   -0.02%     
==========================================
  Files         292      292              
  Lines       33729    33731       +2     
==========================================
- Hits        28936    28932       -4     
- Misses       4793     4799       +6     

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[Hywan]

Thanks for the fix. I think we should also update repeat_vars to not panic when there is nothing to repeat :-].