wp_update() makes category names empty (v 2.6)

[rm53]

Problem: After upgrading an old version (e.g. 2.0) to 2.6 all category names are empty, all slugs are -2 or -2-2 or longer sequences of "-2". Bug: I think I found the bug in function upgrade_230() (upgrade_230 is in /wp-admin/includes/upgrade.php) after these lines:

	foreach ($categories as $category) {
		$term_id = (int) $category->cat_ID;
		$term_group = 0;

the variables $name, $slug and maybe others are NOT set, but some lines later their content is used and written into mysql table as follows:

		$wpdb->query( $wpdb->prepare("INSERT INTO $wpdb->terms (term_id, name, slug, term_group) VALUES 
		(%d, %s, %s, %d)", $term_id, $name, $slug, $term_group) );

the result is IMHO: these fields are empty in the database, see the numerous messages in the support forums about empty category names.

In the same function later on, for link cats the same code is repeated, but with the vars $name etc set correctly:

		foreach ( $link_cats as $category) {
			$cat_id = (int) $category->cat_id;
			$term_id = 0;
			$name = $wpdb->escape($category->cat_name);
			$slug = sanitize_title($name);
			$term_group = 0;

Looks like [7645] broke this.

(In [8350]) Restore fields removed in [7645]. Props rm53. fixes #7320 for trunk

(In [8351]) Restore fields removed in [7645]. Props rm53. fixes #7320 for 2.6