tag_exists(), category_object_exists(), and some tag and cat create fix ups. see #3723

git-svn-id: https://develop.svn.wordpress.org/trunk@5271 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/post.php

@@ -808,7 +808,7 @@ function wp_set_post_tags( $post_id = 0, $tags = '', $append = false ) {
 		$tag = trim( $tag );
 		if ( !$tag_slug = sanitize_title( $tag ) )
 			continue; // discard
-		if ( !$tag_id = category_exists( $tag ) )
+		if ( !$tag_id = tag_exists( $tag ) )
 			$tag_id = wp_create_tag( $tag );
 		$tag_ids[] = $tag_id;
 	}