The "role delete" confirmation page currently reports the wrong number of users assigned to a role, if a user is assigned to the same role in multiple contexts.

Steps to reproduce

1. Create a new role
2. Allow the role to be assigned in the system and category contexts
3. Click 'Assign system roles' and assign the role to a user in the system context
4. Enter the 'Miscellaneous' category and assign the same user the role in the category context
5. Return to define roles and click the delete icon for the test role.

What happens

The confirmation message reads "Currently this role is assigned to 2 users."

What should happen

The confirmation message should read "Currently this role is assigned to 1 users."