Customize: Revert [43619] from the 4.9 branch.

This change is out of the 4.9.x scope, and will be reintroduced in 5.0.x.

See #44809.

git-svn-id: https://develop.svn.wordpress.org/branches/4.9@43702 602fd350-edb4-49c9-b593-d223f7449a82

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

@@ -2284,7 +2284,7 @@ public function validate_setting_values( $setting_values, $options = array() ) {
 			if ( ! is_wp_error( $validity ) ) {
 				/** This filter is documented in wp-includes/class-wp-customize-setting.php */
 				$late_validity = apply_filters( "customize_validate_{$setting->id}", new WP_Error(), $unsanitized_value, $setting );
-				if ( is_wp_error( $late_validity ) && ! empty( $late_validity->errors ) ) {
+				if ( ! empty( $late_validity->errors ) ) {
 					$validity = $late_validity;
 				}
 			}