Fix disappearing category dropdown on new item form

[princekumarg12]

Resolves #4674

Description

This change addresses the issue where the category dropdown disappears after submitting an invalid "New Item" form. The change ensures that the @item_categories variable is correctly populated even after an error occurs, allowing users to select a category without issues.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

The following tests were conducted to verify the changes:

1. Log in as an organization admin.
2. Navigate to the "New Item" page.
3. Attempt to save a blank form.
4. Verify that the category dropdown remains accessible and functional after the error is triggered.

[princekumarg12]

Fixes category dropdown disappearing after new item form error.

[cielf]

Note: this is a PR on an issue that already had a PR on it.

[cielf]

@princekumarg12 There was already a PR in progress for this one, so I think we'll go with that one, if it works.