Custom field filtering not working for cables or virtual chassis

[jeremystretch]

NetBox version

v2.10.9

Python version

3.7

Steps to Reproduce

1. Create a custom field for DCIM > cable
2. Populate the field for one or more cable instances
3. Attempt to filter the cables list using the provided value (e.g. ?cf_foo=123)

Expected Behavior

Only cables with the matching custom field value should be returned. The same thing happens with virtual chassis.

Observed Behavior

The filter has no effect; all cables are returned.