Describe the bug

Moving media to a folder fails with a validation error when using localization with fallback: false and a locale has no alt text. The plugin's custom validate function on the alt field treats all falsy values as invalid on updates (!value || value.trim().length === 0), which blocks folder moves for locales that were never filled in.

Payload fixed locale-aware folder operations in v3.56.0 (payloadcms/payload#13818), but the plugin's custom validate still runs across all locales during the update, causing the operation to fail.

To Reproduce

1. Enable localization with fallback: false and configure the alt-text plugin on a media collection with folders: true
2. Upload a media item and add alt text in the primary locale only (e.g. English), leaving other locales (e.g. Spanish) empty
3. Try to move the media item into a folder via the admin UI
4. See validation error: "An alternate text is required." for the unfilled locale

Expected behavior

Moving media to a folder should succeed regardless of alt text presence in non-active locales. Folder moves are metadata operations and should not trigger content validation.

Package(s) version:

• @jhb.software/payload-alt-text-plugin: 0.4.4
• payload: 3.82.1

Additional context

The issue is in dist/fields/altTextField.js. The validate function rejects null/undefined values (unfilled locales) the same as empty strings (explicitly cleared). A possible fix is to only enforce validation when value is a non-null empty string:

if (value != null && typeof value === 'string' && value.trim().length === 0) {

Workaround: patch the plugin via pnpm patch to set required: false and guard the validate against nullish values.