Avoid a notice in get_the_category_by_ID() when is_wp_error( $term ) is false but $term->name is not set. Clarify the @return value of get_category() and get_tag() which return the same possible types as get_term(), which they wrap.

Props ericmann, SergeyBiryukov.
Fixes #25429.


Built from https://develop.svn.wordpress.org/trunk@27521


git-svn-id: http://core.svn.wordpress.org/trunk@27364 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/category-template.php

@@ -136,9 +136,11 @@ function _usort_terms_by_ID( $a, $b ) {
 function get_the_category_by_ID( $cat_ID ) {
 	$cat_ID = (int) $cat_ID;
 	$category = get_term( $cat_ID, 'category' );
+
 	if ( is_wp_error( $category ) )
 		return $category;
-	return $category->name;
+
+	return ( $category ) ? $category->name : '';
 }
 
 /**