tools: skip check suites with no workflowRun in ci_changes_per_commit.py

[mikeysklar]

What

check_suite["workflowRun"] is null for check suites not attached to a workflow run, such as one whose run was deleted or one belonging to an app integration. get_commit_depth_and_check_suite() indexes into it unconditionally at tools/ci_changes_per_commit.py:158:

if check_suite["workflowRun"]["workflow"]["name"] == "Build CI":

so the scheduler job's "Get last commit with checks" step fails:

Traceback (most recent call last):
  File "tools/ci_changes_per_commit.py", line 241, in <module>
  File "tools/ci_changes_per_commit.py", line 218, in main
  File "tools/ci_changes_per_commit.py", line 158, in get_commit_depth_and_check_suite
TypeError: 'NoneType' object is not subscriptable

When scheduler fails, every downstream job is skipped, so the PR gets no build coverage at all.

Why

An entry with no workflow run can never match "Build CI", so skipping it is the whole fix.

How I tested it

The traceback above is from a real scheduler run on my fork. With the guard, scheduler completes and the downstream jobs run.

No hardware involved. I could not reproduce it on demand, since it depends on which check suites GitHub returns for a given commit.

Scope

One guard, one file. No change to which commit is selected when workflowRun is present.

AI assistance

Written with Claude Code. I reproduced the failure and verified the fix on my own CI.

[dhalbert]

Thanks. Makes sense, though I have never encountered this CI error myself.