[Solved] Error creating items through custom Gui

Mcreator Version: 2023.4.51615

Minecraft Version: 1.20.1 Forge (47.2.0)

Plugins: Nothing.

Summary: 

In the multiplayer, press the button to create an item in the GUI to force it out of the server. 

with this message, Internal Exception: java.lang.NullPointerException: Cannot invoke "net.minecraft.nbt.CompoundTag.getDouble(String)" because "nbt" is null
 

https://drive.google.com/file/d/1ehFaGWG6bbl0gZjABblDcOVFpPc80ODv/view?usp=drive_link

https://drive.google.com/file/d/1HuMNi1JmvKgwL9GSURWPZexz10pLC7vf/view?usp=drive_link

Detail:

I make economy system. 

It works as follows.

1) Player (A) uses the card.
※ It is not a consumable item.

2) The GUI opens.
※ It looks like the following.

<Money : Player current money>
1000k 100k 10k
[button] [button] [button]
1k 100 10
[button] [button] [button]

3) Press [button] as many types as you want.

4) This amount will be reduced from the player's now and money items will be added.

5) Give the added money item to another player (B).

6) Player (B) uses the items received, and the money increases.

But Player(B) Problem occurs in number 3)

Player(B) press [Button] and force it out of the server, with this message 

Internal Exception: java.lang.NullPointerException: Cannot invoke "net.minecraft.nbt.CompoundTag.getDouble(String)" because "nbt" is null

Player(A) has no problem.

※ Player (A) is 'Client' for 'Run Server and Client' in 'Mcreator'

Reference:
https://mcreator.net/forum/93342/item-nbt-works-single-player-crashes-c…

https://mcreator.net/forum/84102/playerpersistant-doesnt-work-servers-properly

※ I couldn't solve the problem even after referring to the two posts.

※ Please let me know if you need photos in your feedback. I will post all the photos you need.