In Rack view "add device" link does not appear when you hover over the rear position

[robbagithub]

Environment

• Python version: 3.6.8
• NetBox version: 2.9.1

Steps to Reproduce

1. Add a non-full-depth device to front of rack in dcim/racks view
2. Open rack elevation view or continue viewing rack in dcim/racks view
3. The "add device" link does not appear when you hover over the rear position

Expected Behavior

Expected to see 'add device' link and able to add a device in same RU in rear. We were able to perform this in 2.7.11 which we upgraded from earlier this week.

Observed Behavior

The 'add device' link did not appear when hovering over the RU in the rear view of the rack

I am still able to add a device if I add the device from the devices view, dcim/devices/add.

[DanSheps]

Discussion here: https://groups.google.com/g/netbox-discuss/c/Ab3-2s7V6zs