Set $post_type to 'any' when taxonomies are involved (code resqued from r15613). See #12891

git-svn-id: http://svn.automattic.com/wordpress/trunk@15649 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/query.php

@@ -1829,6 +1829,13 @@ class WP_Query {
 					}
 				}
 			}
+
+			if ( empty($post_type) ) {
+				$post_type = 'any';
+				$post_status_join = true;
+			} elseif ( in_array('attachment', (array) $post_type) ) {
+				$post_status_join = true;
+			}
 		}
 
 		// Category stuff