fix(app): Render the snapshot header even when a validator summary isn't available

[nellh]

It's rare for a version snapshot to be missing a summary but in this case we should still show the header.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 45.42%. Comparing base (f6d8727) to head (8516b4a).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3850      +/-   ##
==========================================
- Coverage   45.42%   45.42%   -0.01%     
==========================================
  Files         650      650              
  Lines       35013    35012       -1     
  Branches     1711     1720       +9     
==========================================
- Hits        15904    15903       -1     
  Misses      18927    18927              
  Partials      182      182              

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[codecov]

Bundle Report

Changes will decrease total bundle size by 3 bytes (-0.0%) ⬇️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
@openneuro/app-esm	16.14MB	-3 bytes (-0.0%) ⬇️

Affected Assets, Files, and Routes:

view changes for bundle: @openneuro/app-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
assets/dataset-*.js	-3 bytes	388.61kB	-0.0%

Files in assets/dataset-*.js:

• ./src/scripts/dataset/snapshot-container.tsx → Total Size: 11.48kB