Avoid NPE if on SnapshotInfo if 'shallow' boolean not present

[andrross]

I don't have a great answer for how to implement a test here. I don't think there is a way to get the current code to produce a snapshot metadata entry that does not have this remote_store_index_shallow_copy field. It seems like we're missing some more comprehensive backward compatibility testing for snapshots.

Related Issues

Resolves #18187

Check List

• Functionality includes testing.

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[github-actions]

❌ Gradle check result for cfcd98b: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[peternied]

👍

[github-actions]

✅ Gradle check result for 6214878: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 72.64%. Comparing base (70e890a) to head (6214878).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...ch/repositories/blobstore/BlobStoreRepository.java	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #18218      +/-   ##
============================================
+ Coverage     72.52%   72.64%   +0.12%     
- Complexity    67228    67343     +115     
============================================
  Files          5476     5476              
  Lines        310470   310470              
  Branches      45131    45131              
============================================
+ Hits         225168   225552     +384     
+ Misses        66973    66603     -370     
+ Partials      18329    18315      -14     

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[opensearch-trigger-bot]

The backport to 2.19 failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.19 2.19
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.19
# Create a new branch
git switch --create backport/backport-18218-to-2.19
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c32262dce18edd850793a753b3fda894eec23ee0
# Push it to GitHub
git push --set-upstream origin backport/backport-18218-to-2.19
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.19

Then, create a pull request where the base branch is 2.19 and the compare/head branch is backport/backport-18218-to-2.19.