fix(ui): prevent globals crash with arrays fields when lock state user is undefined in handleDocumentLocking (#15259)

### What

Fixes crash when adding items to array fields in Globals that throws
"Cannot read properties of null (reading 'id')".

### Why

When a locked document's user relationship isn't populated (deleted
user, etc.), `lockedState.user` can be `undefined`. The code tried to
access `.id` on this without checking, causing the crash.

### How

- Made `user` field optional in `LockedState` type
- Added null check before accessing `lockedState.user.id` in
`handleDocumentLocking`
- Only process lock state when a valid user exists

Closes #14915

---------

Co-authored-by: Patrik Kozak <35232443+PatrikKozak@users.noreply.github.com>

Author: RajeshKumar11

packages/ui/src/utilities/buildFormState.ts

@@ -22,7 +22,7 @@ import { handlePreview } from './handlePreview.js'
 export type LockedState = {
   isLocked: boolean
   lastEditedAt: string
-  user: ClientUser | number | string
+  user?: ClientUser | number | string
 }
 
 type BuildFormStateSuccessResult = {

packages/ui/src/views/Edit/index.tsx

@@ -209,7 +209,7 @@ export function DefaultEditView({
           ? documentLockState.current?.user?.id
           : documentLockState.current?.user
 
-      if (lockedState) {
+      if (lockedState && lockedState.user) {
         const lockedUserID =
           typeof lockedState.user === 'string' || typeof lockedState.user === 'number'
             ? lockedState.user