When firing following Command

_{if(sender instanceof Player) {
Player player = (Player) sender;
player.openInventory(player.getEnderChest());
return true;
}}

the Server throws following Exception:

java.lang.IndexOutOfBoundsException: Index 31 out of bounds for length 0
at jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64) ~[?:?]
at jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70) ~[?:?]
at jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248) ~[?:?]
at java.util.Objects.checkIndex(Objects.java:372) ~[?:?]
at java.util.ArrayList.get(ArrayList.java:458) ~[?:?]
at net.minecraft.server.v1_14_R1.Container.getSlot(Container.java:170) ~[spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.PlayerConnection.a(PlayerConnection.java:1989) ~[spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.PacketPlayInWindowClick.a(SourceFile:33) ~[spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.PacketPlayInWindowClick.a(SourceFile:10) ~[spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.PlayerConnectionUtils.lambda$0(PlayerConnectionUtils.java:13) ~[spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.TickTask.run(SourceFile:18) ~[spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.IAsyncTaskHandler.h(SourceFile:135) [spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.IAsyncTaskHandlerReentrant.h(SourceFile:23) [spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.IAsyncTaskHandler.p(SourceFile:114) [spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.MinecraftServer.aW(MinecraftServer.java:876) [spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.MinecraftServer.p(MinecraftServer.java:869) [spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.IAsyncTaskHandler.c(SourceFile:123) [spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.MinecraftServer.sleepForTick(MinecraftServer.java:853) [spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:793) [spigot-1.14-pre5.jar:git-Spigot-6dbf995-364b6fb]
at java.lang.Thread.run(Thread.java:834) [?:?]