An error appears in the Item Value widget when, instead of selecting an item, an Item History widget is selected as the source and the Item History widget is later modified (e.g., renamed).

Steps to reproduce:

1. Create a new Item History widget.
2. Create a new Item Value widget.
3. In the Item Value widget configuration, select the Item History widget (from step 1) instead of selecting an item.
4. Change the name of the Item History widget.

Result:
The Item Value widget displays an error.

Expected:

The Item Value widget should handle changes to the referenced Item History widget without throwing an error.