Steps to reproduce:

1. Import the host "test1" host_tags1_tagsExample.yaml
2. Start server, send the following command to create a discovered item

   ./bin/zabbix_sender -z 127.0.0.1 -s "test1" -k "trap1" -o '{"data":[{"{#ITEMNAME}":"item1"}]}' 

3. Open the discovered item's tags tab, switch from Item tags to Inherited and item tags

Result: on top of the form error "Unexpected server error.: TypeError: Cannot set properties of undefined (setting 'counter')" is shown.
Expected: no error when switching between tags and inherited tags.

The error is present no matter if there actually are tags and inherited tags or if they are both not present like in the "test1" example.