From 21aef97ba7efc1f4d7f916b61c6f73f8d3077786 Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <odigiman@gmail.com>
Date: Mon, 1 Jun 2020 12:50:39 +0100
Subject: [PATCH] Player: fixed swapping book pages that only exist
 client-side, closes #3322

---
 src/pocketmine/Player.php | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/pocketmine/Player.php b/src/pocketmine/Player.php
index 20d76562d..950a21f4f 100644
--- a/src/pocketmine/Player.php
+++ b/src/pocketmine/Player.php
@@ -3088,6 +3088,10 @@ class Player extends Human implements CommandSender, ChunkLoader, IPlayer{
 				$modifiedPages[] = $packet->pageNumber;
 				break;
 			case BookEditPacket::TYPE_SWAP_PAGES:
+				if(!$newBook->pageExists($packet->pageNumber) or !$newBook->pageExists($packet->secondaryPageNumber)){
+					//the client will create pages on its own without telling us until it tries to switch them
+					$newBook->addPage(max($packet->pageNumber, $packet->secondaryPageNumber));
+				}
 				$newBook->swapPages($packet->pageNumber, $packet->secondaryPageNumber);
 				$modifiedPages = [$packet->pageNumber, $packet->secondaryPageNumber];
 				break;