fix(dependency_updater): guard against index out of range when branchCommit is empty

[ygd58]

Fixes the issue opened above.

In getVersionAndCommit(), branchCommit[0].SHA is accessed directly without checking if the GitHub API returned any commits. If the branch exists but has no commits, or if the API returns an empty list, this panics with index out of range.

Added a len(branchCommit) == 0 check that returns a descriptive error naming the branch and repo instead of panicking.

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[ygd58]

hey @meyer9@danyalprout can you take a look? guards against an index out of range panic when the GitHub API returns zero commits for a branch in the dependency updater.