No baseobjects available to link to ethernets

### Steps to reproduce

Networks -> IP Addresses : Add ip address
Press "add ethernet" button (green plus sign)
Click on base object find icon.

### Expected behavior

A list of base objects to select

### Actual behavior

An empty list but the counter of the bottom is reflecting base objects

### Environment

dpkg -l:
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description

ii ralph-core 20210525.1 amd64 Ralph is an DCIM/CMDB - asset management for Data Centers/ Back Office.

Distributor ID: Ubuntu
Description: Ubuntu 18.04.5 LTS
Release: 18.04
Codename: bionic

Linux ralph3pro 4.15.0-143-generic #147-Ubuntu SMP Wed Apr 14 16:10:11 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

* Ralph version: 20210525.1
* Operating system: Ubuntu 18.04.5 LTS
* Method of installation: Deb package? Manual installation? Docker? deb package