fix: migrator recover from v2 nulls

[JR-Morgan]

V2 has nulls everywhere

[JR-Morgan]

This change isn't worth deploying on its own, it's v2 edge-cases only.

I'm leaving it parked here waiting for a more critical fix to justify updating the migrator.

[codecov]

Codecov Report

❌ Patch coverage is 10.52632% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.53%. Comparing base (03f34b6) to head (5cafeb7).

Files with missing lines	Patch %	Lines
...Sdk.BundleMigrator/Migration/PipelineExtensions.cs	10.52%	11 Missing and 6 partials ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##           big-truck     #559      +/-   ##
=============================================
- Coverage      69.54%   69.53%   -0.02%     
=============================================
  Files            436      436              
  Lines          23536    23541       +5     
  Branches        2315     2320       +5     
=============================================
  Hits           16369    16369              
- Misses          6374     6377       +3     
- Partials         793      795       +2     

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