When a search triggers controlled vocabulary expansion but the expansion term contributes zero results, Primo VE still displays the message informing the user that the search has been expanded, and offers a link to disable the expansion (conVoc=false).

Clicking this link produces no observable change in the result set, since the expansion was not contributing any results in the first place.

This creates a confusing experience for the user:
1. The system implies the search was meaningfully expanded
2. The user is offered the option to opt out
3. Opting out has no visible effect

Proposed improvement:
The expansion notification and opt-out link should only be displayed when the controlled vocabulary expansion actually contributes results. If the expansion term returns zero results, the notification should be suppressed — or alternatively, the UI should clearly communicate that the expansion had no impact on the current result set.

This would make the interface more transparent and trustworthy, and avoid users wondering whether the opt-out functionality is broken.