Player join server error

[WetABQ]

Issue Description

java.lang.NoSuchMethodError: cn.nukkit.AdventureSettings.setCanFly(Z)V at world.protect.Listener.EventListener.setGamemode(EventListener.java:62) at world.protect.Listener.EventListener.setIf(EventListener.java:68) at world.protect.Listener.EventListener.onPlayerJoinEvent(EventListener.java:57) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at cn.nukkit.plugin.MethodEventExecutor.execute(MethodEventExecutor.java:29) ... 10 more

Steps to Reproduce the Issue

1. join server

OS and Versions

• Nukkit Version: ??
• Java Version:

  ??

• Host Configuration:

Item	Value
Host OS	??
Memory(RAM)	?? GB
Storage Size	?? GB
Storage Type	??
CPU Type	??
CPU Core Count	?? cores ?? threads
Upstream Bandwidth	??

• Client Configuration:

Item	Value
Client Edition	??
Client Version	??

Crashdump, Backtrace or Other Files

java.lang.NoSuchMethodError: cn.nukkit.AdventureSettings.setCanFly(Z)V at world.protect.Listener.EventListener.setGamemode(EventListener.java:62) at world.protect.Listener.EventListener.setIf(EventListener.java:68) at world.protect.Listener.EventListener.onPlayerJoinEvent(EventListener.java:57) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at cn.nukkit.plugin.MethodEventExecutor.execute(MethodEventExecutor.java:29) ... 10 more

[WetABQ]

And how to add an ElementButton in WindowCustom?

[Creeperface01]

Its a plugin issue