I'm having some problems to make the plugin work in 1.18.2.
I usually try to find a fix by my self but i was not successfull this time.
It was working fine with the 1.16.5 version of minecraft and 9.1.2.

I'm using Paper version git-Paper-234 (MC: 1.18.2) (API version 1.18.2-R0.1-SNAPSHOT) (Git: c34fb09)

The plugin seens to "load" but not completely.
This is what shows up at start:

Exception in thread "Thread-16" java.util.NoSuchElementException: No value present
[01:27:40 WARN]: at java.base/java.util.Optional.get(Optional.java:143)
[01:27:40 WARN]: at GUIShop-9.1.6.jar//com.pablo67340.guishop.definition.ShopItem.determineHighestSlots(ShopItem.java:26)
[01:27:40 WARN]: at GUIShop-9.1.6.jar//com.pablo67340.guishop.listenable.Shop.loadItems(Shop.java:138)
[01:27:40 WARN]: at GUIShop-9.1.6.jar//com.pablo67340.guishop.GUIShop.warmup(GUIShop.java:600)
[01:27:40 WARN]: at GUIShop-9.1.6.jar//com.pablo67340.guishop.GUIShop.handleShopsConfig(GUIShop.java:478)
[01:27:40 WARN]: at java.base/java.lang.Thread.run(Thread.java:833)

and

[01:27:41 WARN]: Exception in thread "Thread-11" java.lang.NullPointerException: Cannot invoke "org.bukkit.configuration.ConfigurationSection.getValues(boolean)" because the return value of "org.bukkit.configuration.file.FileConfiguration.getConfigurationSection(String)" is null
[01:27:41 WARN]: at GUIShop-9.1.6.jar//com.pablo67340.guishop.GUIShop.loadDefaults(GUIShop.java:424)
[01:27:41 WARN]: at GUIShop-9.1.6.jar//com.pablo67340.guishop.GUIShop.handleConfig(GUIShop.java:465)
[01:27:41 WARN]: at java.base/java.lang.Thread.run(Thread.java:833)

And trying to reload the plugin in game also don't work (attached file)
guiShop_ReloadError.txt

Any help will be appreciated.