fix: Fix panic when joining with empty frame (debug only)

[lukemanley]

closes #19863

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.43%. Comparing base (9ceedde) to head (2a6bbf8).
Report is 46 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19896      +/-   ##
==========================================
- Coverage   79.52%   79.43%   -0.09%     
==========================================
  Files        1546     1554       +8     
  Lines      213515   215611    +2096     
  Branches     2444     2452       +8     
==========================================
+ Hits       169803   171278    +1475     
- Misses      43162    43775     +613     
- Partials      550      558       +8     

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