[Backport 1.3.latest] Partial parsing bug with empty schema file

[leahwicz]

Description

Backport ##6494

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[github-actions]

The backport to 1.2.latest failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.2.latest 1.2.latest
# Navigate to the new working tree
cd .worktrees/backport-1.2.latest
# Create a new branch
git switch --create backport-6505-to-1.2.latest
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 6e9ff280e2d1c2b7962da5c15a860f47bced3784
# Push it to GitHub
git push --set-upstream origin backport-6505-to-1.2.latest
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.2.latest

Then, create a pull request where the base branch is 1.2.latest and the compare/head branch is backport-6505-to-1.2.latest.