Ticket #21760: 21760.11.patch

wp-includes/taxonomy.php

@@ -831 +831 @@
 function get_term_by( $field, $value, $taxonomy = '', $output = OBJECT, $filter = 'raw' ) {
 
         // 'term_taxonomy_id' lookups don't require taxonomy checks.
-        if ( 'term_taxonomy_id' !== $field && ! taxonomy_exists( $taxonomy ) ) {
+        if ( 'term_taxonomy_id' !== $field && ! taxonomy_exists( $taxonomy ) || empty( $value ) ) {
                 return false;
         }