Fix transfering groups to root for EE

What does this MR do?

When transferring a group to the root we got an error undefined method root_ancestor' for nil:NilClassbecause we have a checkgroup.root_ancestor == new_parent_group.root_ancestor`. This check runs only if packages feature is available (EE).

This MR fixes that.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.