Form-level validation with onChange and arrays throws an undefined errorMap

Describe the bug

Form-level validation with onChange and arrays throws an undefined errorMap when all fields are deleted or when a single field is removed. This issue only occurs with form-level validation using the onChange validator.

Uncaught TypeError: Cannot read properties of undefined (reading 'errorMap')
    at @tanstack_react-form.js?v=473e5c45:1136:27
    at functionalUpdate (@tanstack_react-form.js?v=473e5c45:423:42)
    at @tanstack_react-form.js?v=473e5c45:1349:22
    at Store.setState (@tanstack_react-form.js?v=473e5c45:296:22)
    at FormApi.setFieldMeta (@tanstack_react-form.js?v=473e5c45:1344:22)
    at @tanstack_react-form.js?v=473e5c45:1133:20
    at batch (@tanstack_react-form.js?v=473e5c45:255:5)
    at FormApi.validateSync (@tanstack_react-form.js?v=473e5c45:1090:7)
    at FieldApi.validate (@tanstack_react-form.js?v=473e5c45:2205:97)
    at FormApi.validateField (@tanstack_react-form.js?v=473e5c45:1080:28)

Your minimal, reproducible example

https://stackblitz.com/edit/vitejs-vite-egzzxehs?file=src%2FApp.tsx

Steps to reproduce

1. Make a change in the form to trigger onChange event (you must see validation error for both fields)

2. Click on clear all or clean one
3. See console logs

TanStack Form version

1.19.2

TypeScript version

5.8.3

Start with the linked StackBlitz reproduction using TanStack Form 1.19.2 and follow the stack trace through FormApi.validateField, validateSync, and setFieldMeta. Compare form-level onChange validation when clearing all fields versus one array item; done means deletion no longer throws an undefined errorMap.