fix: Handle index queries where child found without parent

[AndrewSisley]

Relevant issue(s)

Resolves #2925

Description

Handles secondary index queries where child found without parent.

Previously the new test would panic further up the callstack (to the prod change), as the parent doc would be nil minus the joined property.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.27%. Comparing base (a4029a9) to head (531096d).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2942      +/-   ##
===========================================
- Coverage    79.33%   79.27%   -0.05%     
===========================================
  Files          326      326              
  Lines        24860    24862       +2     
===========================================
- Hits         19721    19709      -12     
- Misses        3728     3737       +9     
- Partials      1411     1416       +5     

Flag	Coverage Δ
all-tests	79.27% <100.00%> (-0.05%)	⬇️

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

Files	Coverage Δ
internal/planner/type_join.go	81.33% <100.00%> (+0.09%)	⬆️

... and 17 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a4029a9...531096d. Read the comment docs.

[fredcarle]

LGTM!