Steps to reproduce:

1. open form for creating/editing the item with "Zabbix trapper" type;
2. fill in all the required properties
3. fill '127.0.0.1' for the "Allowed hosts" input
4. Click Add/Update button

Result:
Open created/updated Trapper item - "Allowed hosts" is empty
Expected:
The "Allowed hosts" value is '127.0.0.1'.