Bug 36371: Check if patron attribute is defined in circ-menu.inc

Bug 36371: Check if patron attribute is defined in circ-menu.inc

This patch changes the conditional that determines if a patron attribute is displayed in the patron brief info. Instead of checking the value of the attribute we should check if the attribute is defined.

To test:
1. Create a patron attribute, eg. party_mode, check 'display in patron's brief info' and tie to the YES_NO authorised value.
2. Find a patron and set your attribute to Yes
3. Confirm you see the attribute and its value both in the "Additional attributes and identifiers" section of the patron detail page and in the patron brief info area
4. Set your attribute to No
5. Confirm you see the attribute and its value in "Additional attributes and identifiers" but it no longer shows in the brief info
6. Apply patch and restart_all
7. Notice that your attribute now displays in the brief info, such as Party mode: No
8. Set the attribute to the first empty option
9. Check the patron record brief info to confirm that the attribute does not display when the value is empty.

Signed-off-by: Andrew Fuerste Henry <andrewfh@dubcolib.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>