Error when players try to join a created game

[quickusername]

This error is displayed in the console when any player tries to join an already created game:

Could not pass event InventoryClickEvent to CoinFlipper v2.92

org.bukkit.event.EventException: null

at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:319) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:589) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:576) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.PlayerConnection.a(PlayerConnection.java:2277) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.PacketPlayInWindowClick.a(SourceFile:32) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.PacketPlayInWindowClick.a(SourceFile:10) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.PlayerConnectionUtils.lambda$0(PlayerConnectionUtils.java:19) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.TickTask.run(SourceFile:18) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.executeTask(SourceFile:144) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.IAsyncTaskHandlerReentrant.executeTask(SourceFile:23) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.executeNext(SourceFile:118) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.MinecraftServer.bb(MinecraftServer.java:942) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.MinecraftServer.executeNext(MinecraftServer.java:935) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.executeAll(SourceFile:103) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.MinecraftServer.sleepForTick(MinecraftServer.java:918) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:851) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$0(MinecraftServer.java:164) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]

Caused by: java.lang.NumberFormatException: For input string: ""

at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65) ~[?:1.8.0_212]

at java.lang.Integer.parseInt(Integer.java:592) ~[?:1.8.0_212]

at java.lang.Integer.parseInt(Integer.java:615) ~[?:1.8.0_212]

at io.github.gronnmann.utils.coinflipper.GeneralUtils.getIntInString(GeneralUtils.java:10) ~[?:?]

at io.github.gronnmann.coinflipper.gui.SelectionScreen.detectClicks(SelectionScreen.java:173) ~[?:?]

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_212]

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_212]

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_212]

at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_212]

at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:315) ~[spigot-1.16.4.jar:git-Spigot-ff439d1-ff2b944]

... 18 more