Fixes duplicate tree view add button for closed Controlled Vocabularies

[aseyedia]

References

Fixes #3325

Description

The Controlled Vocabulary tree view was displaying two "Add" buttons, one enabled and one disabled, for closed Controlled Vocabularies.

You can read more here.

Instructions for Reviewers

Minor change. I just removed one of the excess buttons and moved the conditional logic to the [disabled] parameter in the button class.

To test it, try opening up a closed Controlled Vocabulary tree view and observing the "Add" button to make sure it's disabled and that there's only one of them.

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[aseyedia]

@tdonohue I can port this change if it gets approved, unless I need to port it first, in which case, I will do that.

[tdonohue]

@aseyedia : You do not need to port this PR prior to review. In fact, we have an automated porting process which is triggered if we merge a PR with a port to [branch] label. This automated process usually works well for small PRs (like this one), but will sometimes fail. So, we'd only ask you to port this PR yourself if we find that automated process fails.

[github-actions]

Hi @aseyedia,
Conflicts have been detected against the base branch.
Please resolve these conflicts as soon as you can. Thanks!