"'DeviceBayForm' has no field named 'installed_device'" when trying to edit device bay details with an installed device in it

[hoalex]

Environment

• Python version: 3.6.8
• NetBox version: 2.6.9

Steps to Reproduce

1. Create Device Type "Parent" with Parent/child status = Parent and add one device bay "Bay 1"
2. Create Device Type "Child" with Parent/child status = Child
3. Create Devices "Parent" and "Child"
4. Assign device "Child" to bay of device "Parent"
5. Navigate to device "Parent" and select the "Edit device bay" icon for "Bay 1"
6. Do not change anything in the form, simply click on "Update"

Error message appears:

Expected Behavior

No error message when trying to update the details of an installed device in a device bay.

Observed Behavior

Changing details of a device bay only seems to be possible as long as the device bay has a status of "Vacant". Once a device is installed in the device bay, the above error message appears.