Skip nodes where published_version is not present

[entantoencuanto]

:v: What does this PR do?

This PR prevents exceptions that happen when a project of a Plan is published but its published version is not set. This should not happen (published without version) but the exception can be prevented since it is related with a scope that should only operate on projects with a published version. The PR causes projects without a published version to be ignored from this scope.

:mag: How should this be manually tested?

:eyes: Screenshots

Before this PR

After this PR

:shipit: Does this PR changes any configuration file?

• [ ] new environment variable in .env.example?
• [ ] new entry in config/application.yml?
• [ ] new entry in config/secrets.yml?

(Changes in these files might need to update the role in Ansible)

:book: Does this PR require updating the documentation?

• [ ] new site configuration variable?
• [ ] new site template?
• [ ] new module/submodule settings?
• [ ] significant changes in some feature?