fix: Some quick fixes to make walk_back work

[effigies]

Experimenting with this to chat with @yarikoptic.

@ubdbra001 I won't merge this to avoid conflicting with your work, but you may feel free to merge it or cherry-pick anything into your PR.

[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.68%. Comparing base (9faf0e3) to head (fffe298).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/bids_validator/context.py	75.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #35      +/-   ##
==========================================
+ Coverage   86.21%   89.68%   +3.46%     
==========================================
  Files          12       12              
  Lines         624      630       +6     
  Branches      103      104       +1     
==========================================
+ Hits          538      565      +27     
+ Misses         65       42      -23     
- Partials       21       23       +2     

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[ubdbra001]

I had a look and it seems good to me, happy for you to merge to main and I'll merge into my branch