Coding Standards: Remove redundant check in WP_Customize_Widgets.

`isset()` is enough to check for the property existence here.

Follow-up to [60279].

See #63168.

git-svn-id: https://develop.svn.wordpress.org/trunk@60290 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/class-wp-customize-widgets.php

@@ -923,7 +923,7 @@ public function output_widget_control_templates() {
 					<span class="customize-action">
 						<?php
 						$panel       = $this->manager->get_panel( 'widgets' );
-						$panel_title = $panel && isset( $panel->title ) ? $panel->title : __( 'Widgets' );
+						$panel_title = isset( $panel->title ) ? $panel->title : __( 'Widgets' );
 						/* translators: &#9656; is the unicode right-pointing triangle. %s: Section title in the Customizer. */
 						printf( __( 'Customizing &#9656; %s' ), esc_html( $panel_title ) );
 						?>