Paper/nms-patches/ItemWrittenBook.patch

--- a/net/minecraft/server/ItemWrittenBook.java
+++ b/net/minecraft/server/ItemWrittenBook.java
@@ -61,6 +61,23 @@
 
                         Object object;
 
+                        // CraftBukkit start
+                        // Some commands use the worldserver variable but we leave it full of null values,
+                        // so we must temporarily populate it with the world of the commandsender
+                        WorldServer[] prev = MinecraftServer.getServer().worldServer;
+                        MinecraftServer server = MinecraftServer.getServer();
+                        server.worldServer = new WorldServer[server.worlds.size()];
+                        server.worldServer[0] = (WorldServer) entityhuman.getWorld();
+                        int bpos = 0;
+                        for (int pos = 1; pos < server.worldServer.length; pos++) {
+                            WorldServer world = server.worlds.get(bpos++);
+                            if (server.worldServer[0] == world) {
+                                pos--;
+                                continue;
+                            }
+                            server.worldServer[pos] = world;
+                        }
+                        // CraftBukkit end
                         try {
                             IChatBaseComponent ichatbasecomponent = IChatBaseComponent.ChatSerializer.b(s);
 
@@ -68,6 +85,7 @@
                         } catch (Exception exception) {
                             object = new ChatComponentText(s);
                         }
+                        finally { MinecraftServer.getServer().worldServer = prev; } // CraftBukkit
 
                         nbttaglist.a(i, new NBTTagString(IChatBaseComponent.ChatSerializer.a((IChatBaseComponent) object)));
                     }