0. ALWAYS PROVIDE INFORMATION ABOUT MODLOADER (Fabric / Forge) AND MOD VERSION (For Example 1.19.2-8.2.10)
   Minecraft 1.21 with Fabric Loader 0.15.11
   travelersbackpack-fabric-1.21-10.0.2 Tried updating to latest version fabric-1.21.1-10.0.3 but issue persists.

1. Describe the bug
   Lost connection from singleplayer world after creating reserved places for enchanted item in backpack.
   When attempting to open the world again, I either get "Disconnected" to server list or Connection Lost. (lost connection: Internal Exception: io.netty.handler.codec.EncoderException: Failed to encode packet 'clientbound/minecraft:container_set_content')

2. Write steps to reproduce the bug

Tested with an Enchanted Golden Helmet

• [1] Place an enchanted item into backpack slot,
• [2] Enter select mode to "Choose slot with item to reserve place for this item",
• [3] Reserve a backpack slot for the enchanted item,
• [4] Exit select mode, game should disconnect with Connection Lost.
  Trying to play the world should result in the same Connection Lost error.

4. What is expected behaviour
   Enter select mode, Reserve slot for item, Exit select mode, Close backpack
   The world save shouldn't be corrupted

5. Screenshots (If applicable)
   Error Log
   https://pastebin.com/DPHBehaK

https://www.curseforge.com/minecraft/mc-mods/travelers-backpack-fabric/files/5498352