Delay calling is_using_gutenberg until `use_block_editor_for_post_t…

…ype` is defined.

includes/syndicated-post-ui.php

@@ -7,6 +7,8 @@
 
 namespace Distributor\SyndicatedPostUI;
 
+use Distributor\Utils;
+
 /**
  * Setup actions and filters
  *
@@ -26,12 +28,8 @@ function() {
 			add_filter( 'admin_body_class', __NAMESPACE__ . '\add_linked_class' );
 			add_filter( 'post_row_actions', __NAMESPACE__ . '\remove_quick_edit', 10, 2 );
 
-			$post = isset( $_GET['post'] ) ? get_post( (int) $_GET['post'] ) : false; // @codingStandardsIgnoreLine Nonce not required
-
-			if ( $post && ! \Distributor\Utils\is_using_gutenberg( $post ) ) {
-				add_action( 'do_meta_boxes', __NAMESPACE__ . '\replace_revisions_meta_box', 10, 3 );
-				add_action( 'add_meta_boxes', __NAMESPACE__ . '\add_revisions_meta_box' );
-			}
+			add_action( 'do_meta_boxes', __NAMESPACE__ . '\replace_revisions_meta_box', 10, 3 );
+			add_action( 'add_meta_boxes', __NAMESPACE__ . '\add_revisions_meta_box' );
 
 			add_action( 'admin_init', __NAMESPACE__ . '\setup_columns' );
 		}
@@ -256,6 +254,10 @@ function replace_revisions_meta_box( $post_type, $context, $post ) {
 		return;
 	}
 
+	if ( Utils\is_using_gutenberg( $post ) ) {
+		return;
+	}
+
 	$original_blog_id   = get_post_meta( $post->ID, 'dt_original_blog_id', true );
 	$original_post_id   = get_post_meta( $post->ID, 'dt_original_post_id', true );
 	$original_source_id = get_post_meta( $post->ID, 'dt_original_source_id', true );