DM-34616: Ensure implied dimensions are not null in test data IDs.

[TallJimbo]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Merging #247 (06c679f) into main (703ef5c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #247   +/-   ##
=======================================
  Coverage   72.14%   72.15%           
=======================================
  Files          60       60           
  Lines        6628     6629    +1     
  Branches     1250     1250           
=======================================
+ Hits         4782     4783    +1     
  Misses       1621     1621           
  Partials      225      225           

Impacted Files	Coverage Δ
tests/test_testUtils.py	98.10% <100.00%> (+<0.01%)	⬆️
python/lsst/pipe/base/graph/graph.py	81.23% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 703ef5c...06c679f. Read the comment docs.

[kfindeisen]

It looks like I can't revoke approval, but I meant the above approval to be contingent on lsst/daf_butler#680 not having an alternative solution.

[TallJimbo]

Changes to daf_butler on this ticket now make this branch unnecessary.