fix(next): viewing modified-only diff view containing localized arrays throws error (#11006)

Fixes https://github.com/payloadcms/payload/issues/11002

`buildVersionFields` was adding `null` version fields to the version fields array. When RenderVersionFieldsToDiff tried to render those, it threw an error.

This PR ensures no `null` fields are added, as `RenderVersionFieldsToDiff` can't process them. That way, those fields are properly skipped, which is the intent of `modifiedOnly`

test/versions/e2e.spec.ts

@@ -960,6 +960,18 @@ describe('Versions', () => {
       )
     })
 
+    test('correctly renders modified-only diff for localized array fields', async () => {
+      await navigateToVersionFieldsDiff()
+
+      const textInArrayES = page.locator('[data-field-path="arrayLocalized"][data-locale="es"]')
+
+      await expect(textInArrayES).toContainText('No Array Localizeds found')
+
+      await page.locator('#modifiedOnly').click()
+
+      await expect(textInArrayES).toBeHidden()
+    })
+
     test('correctly renders diff for block fields', async () => {
       await navigateToVersionFieldsDiff()