Quick/Bulk Edit: Ensure that $post_ids variable is initialized ahead of usage.

This brings some consistency between similar fragments of `wp-admin/edit.php` and `wp-admin/upload.php`.

Follow-up to [51111], [51161].

See #39589, #53411.

git-svn-id: https://develop.svn.wordpress.org/trunk@51163 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/edit.php

@@ -80,6 +80,8 @@ if ( $doaction ) {
 		$sendback = admin_url( $post_new_file );
 	}
 
+	$post_ids = array();
+
 	if ( 'delete_all' === $doaction ) {
 		// Prepare for deletion of all posts with a specified post status (i.e. Empty Trash).
 		$post_status = preg_replace( '/[^a-z0-9_-]+/i', '', $_REQUEST['post_status'] );
@@ -96,7 +98,7 @@ if ( $doaction ) {
 		$post_ids = array_map( 'intval', $_REQUEST['post'] );
 	}
 
-	if ( ! isset( $post_ids ) ) {
+	if ( empty( $post_ids ) ) {
 		wp_redirect( $sendback );
 		exit;
 	}