Resolve #239801 "Fix bug when go.sum does not exist"

What does this MR do?

This MR fixes a bug that caused license finder to fail when scanning a go project without a go.sum file

What are the relevant issue numbers?

gitlab-org/gitlab#239801 (closed)

Testing

• Before change, license scanning fails, as shown here
• After change, license scanning passes, as shown here

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Job definition example
  • CI Templates (to be removed)
  • Vendored CI Templates (also in CE)
  • Ensure that all of the ENV vars supported are propagated to Docker containers upon docker run in job definitions
• Conforms to the code review guidelines
• Security reports checked/validated by reviewer

Closes #239801