Not working on 1.16.5

[hardcorefactions]

I already checked many ways but it still gives an error.

[19:17:51] [Server thread/ERROR]: Could not pass event PlayerJoinEvent to Vorex v1.0-SNAPSHOT
org.bukkit.event.EventException: null
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:310) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:589) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:576) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.PlayerList.a(PlayerList.java:267) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.LoginListener.c(LoginListener.java:173) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.LoginListener.tick(LoginListener.java:71) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.NetworkManager.a(NetworkManager.java:229) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.ServerConnection.c(ServerConnection.java:143) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.MinecraftServer.b(MinecraftServer.java:1246) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.DedicatedServer.b(DedicatedServer.java:394) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.MinecraftServer.a(MinecraftServer.java:1127) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:966) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$0(MinecraftServer.java:273) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at java.lang.Thread.run(Thread.java:750) [?:?]
Caused by: java.lang.IllegalArgumentException: Display name cannot be null
        at org.apache.commons.lang.Validate.notNull(Validate.java:192) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at org.bukkit.craftbukkit.v1_16_R3.scoreboard.CraftObjective.setDisplayName(CraftObjective.java:43) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        at io.github.thatkawaiisam.assemble.AssembleBoard.getObjective(AssembleBoard.java:62) ~[?:?]
        at io.github.thatkawaiisam.assemble.AssembleBoard.setup(AssembleBoard.java:77) ~[?:?]
        at io.github.thatkawaiisam.assemble.AssembleBoard.<init>(AssembleBoard.java:35) ~[?:?]
        at io.github.thatkawaiisam.assemble.AssembleListener.onPlayerJoin(AssembleListener.java:35) ~[?:?]
        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 org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:306) ~[spigot-1.16.5.jar:3096a-Spigot-9fb885e-af1a232]
        ... 14 more