General: Fix code quality issues which were identified by static analysis.

This fixes minor issues that could cause PHP notices under the right conditions, and fixes some general incorrectness.

Props jrf, hellofromTonya for review

See #52217

Built from https://develop.svn.wordpress.org/trunk@51850


git-svn-id: http://core.svn.wordpress.org/trunk@51449 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/widgets/class-wp-widget-tag-cloud.php

@@ -53,6 +53,8 @@ class WP_Widget_Tag_Cloud extends WP_Widget {
 			}
 		}
 
+		$default_title = $title;
+
 		$show_count = ! empty( $instance['count'] );
 
 		$tag_cloud = wp_tag_cloud(