SPIGOT-4478: NPE during PlayerLoginEvent recipe manipulation

nms-patches/RecipeBookServer.patch

@@ -17,3 +17,11 @@
                  this.a(minecraftkey);
                  this.c(minecraftkey);
                  arraylist.add(minecraftkey);
+@@ -61,6 +62,7 @@
+     }
+ 
+     private void a(PacketPlayOutRecipes.Action packetplayoutrecipes_action, EntityPlayer entityplayer, List<MinecraftKey> list) {
++        if (entityplayer.playerConnection == null) return; // SPIGOT-4478 during PlayerLoginEvent
+         entityplayer.playerConnection.sendPacket(new PacketPlayOutRecipes(packetplayoutrecipes_action, list, Collections.emptyList(), this.c, this.d, this.e, this.f));
+     }
+