Undefined index when creating dependent item for item prototype

Steps to reproduce:

1. Get fresh Zabbix master (currently commit f5615ce5b8fa5)
2. Configuration -> Templates -> Create new template AAA
3. Add new discovery rule D1 to AAA
4. Add item prototype to D1
4. In the list of item prototypes click "..." (Wizard) and select "Create dependent item"

Result:

Expected:
No error