[Server thread/ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'npcbook' in plugin CitizensBooks v2.5.6
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:47) ~[patched_1.15.2.jar:git-Paper-103]
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:159) ~[patched_1.15.2.jar:git-Paper-103]
	at org.bukkit.craftbukkit.v1_15_R1.CraftServer.dispatchCommand(CraftServer.java:742) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.PlayerConnection.handleCommand(PlayerConnection.java:1821) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.PlayerConnection.a(PlayerConnection.java:1629) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.PacketPlayInChat.a(PacketPlayInChat.java:47) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.PacketPlayInChat.a(PacketPlayInChat.java:5) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.PlayerConnectionUtils.lambda$ensureMainThread$0(PlayerConnectionUtils.java:23) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.TickTask.run(SourceFile:18) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeTask(IAsyncTaskHandler.java:136) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.IAsyncTaskHandlerReentrant.executeTask(SourceFile:23) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeNext(IAsyncTaskHandler.java:109) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.MinecraftServer.ba(MinecraftServer.java:1038) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.MinecraftServer.executeNext(MinecraftServer.java:1031) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.awaitTasks(IAsyncTaskHandler.java:119) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.MinecraftServer.sleepForTick(MinecraftServer.java:1015) ~[patched_1.15.2.jar:git-Paper-103]
	at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:938) ~[patched_1.15.2.jar:git-Paper-103]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_201]
Caused by: java.lang.NullPointerException
	at java.util.Optional.orElseGet(Optional.java:267) ~[?:1.8.0_201]
	at ro.nicuch.citizensbooks.CitizensBooksAPI.getPlayer(CitizensBooksAPI.java:289) ~[?:?]
	at ro.nicuch.citizensbooks.CitizensBooksCommand.onCommand(CitizensBooksCommand.java:68) ~[?:?]
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45) ~[patched_1.15.2.jar:git-Paper-103]
	... 17 more