Bug 31086: Prevent placing hold with no pickup location

Bug 31086: Prevent placing hold with no pickup location

To test:
1 - Apply patch
2 - Repeat test on previous patch
3 - You should get a warning popup when attempting to save hold
4 - Reload page
5 - Inspect the HTML and manualy set #pickup value of selected option to ""
6 - Attempt to save hold
7 - You get the popup
8 - Place a hold normally (with location) and verify it works

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>