While modifying scenario settings, the "Context items" widget shows improper behaviour. The widget contains a hand glass icon. When the user clicks on the icon, the page reloads and then throws "502 Bad gateway" error.

Steps to reproduce:
1. Open Personalization > Scenarios tab in the Ibexa platform.
2. Edit a scenario which contains a collaborative model.
3. In the "Context items" widget - click on the hand glass.

Result: