category slug field is invisible, how to enable it?

category slug field is invisible, how to enable it? i have looked source, and i see that showing the field is under condition of global_terms_enabled() is false.
i say about page wp-admin/edit-tags.php?taxonomy=category .
the code is

<?php if ( ! global_terms_enabled() ) : ?>
<div class="form-field">
	<label for="tag-slug"><?php _ex('Slug', 'Taxonomy Slug'); ?></label>
	<input name="slug" id="tag-slug" type="text" value="" size="40" />
	<p><?php _e('The “slug” is the URL-friendly version of the name. It is usually all lowercase and contains only letters, numbers, and hyphens.'); ?></p>
</div>
<?php endif; // is_multisite() ?>

may be useful to you to help me:

when i have searched “wordpress category slug field” with google i have found: https://wordpress.stackexchange.com/questions/2919/category-slug-field-missing-with-registered-custom-taxonomy

i had installed sitepress multilingual cms, but it is deactivated now, maybe it has registered custom taxonomy? if so how to delete its custom taxonomy?