Validation.js raises "Cannot read properties of undefined" error

[boris-burgos]

Description

When a <Query> component's fields are updated while a condition still references a removed field, an "Uncaught TypeError: Cannot read properties of undefined" is thrown, causing the component to crash.

Reproduction

Live example: Netlify demo
Source code: GitHub

Steps:

1. Click "Add group".
2. Select "Test group" in the group selector.
3. Select "Number field" in the field selector.
4. Click "Clear" near the top-left selector to remove the group's fields.
5. Component crashes.

Expected behavior

The component should not crash. Removed fields should be handled gracefully, keeping the component functional.

Example of correct behavior: Netlify demo

Additional context

The issue originates in validation.js where item becomes undefined.