errors

steynvaart issued server command: /eh book steynvaart
[09:55:13] [Server thread/INFO]: steynvaart issued server command: /deop steynvaart
[09:55:36] [Server thread/INFO]: Made steynvaart a server operator
[09:56:16] [Server thread/WARN]: [EpicHoppers] Task #10 for EpicHoppers vmaven-version-number generated an exception
java.lang.NullPointerException: null
	at com.songoda.epichoppers.storage.serializers.HopperSerializer.serialize(HopperSerializer.java:69) ~[?:?]
	at com.songoda.epichoppers.storage.serializers.HopperSerializer.serialize(HopperSerializer.java:20) ~[?:?]
	at com.google.gson.internal.bind.TreeTypeAdapter.write(TreeTypeAdapter.java:81) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at com.google.gson.Gson.toJson(Gson.java:669) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at com.google.gson.Gson.toJson(Gson.java:648) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at com.google.gson.Gson.toJson(Gson.java:603) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at com.songoda.epichoppers.storage.Database.serialize(Database.java:37) ~[?:?]
	at com.songoda.epichoppers.storage.SQLiteDatabase.save(SQLiteDatabase.java:74) ~[?:?]
	at com.songoda.epichoppers.EpicHoppersPlugin.lambda$saveToFile$2(EpicHoppersPlugin.java:307) ~[?:?]
	at java.util.HashMap.forEach(Unknown Source) ~[?:1.8.0_181]
	at java.util.Collections$UnmodifiableMap.forEach(Unknown Source) ~[?:1.8.0_181]
	at com.songoda.epichoppers.EpicHoppersPlugin.saveToFile(EpicHoppersPlugin.java:307) ~[?:?]
	at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftTask.run(CraftTask.java:81) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:391) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at net.minecraft.server.v1_13_R2.MinecraftServer.b(MinecraftServer.java:893) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at net.minecraft.server.v1_13_R2.DedicatedServer.b(DedicatedServer.java:417) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:835) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:733) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_181]
[09:57:21] [Server thread/INFO]: steynvaart issued server command: /time day
[10:01:17] [Server thread/WARN]: [EpicHoppers] Task #10 for EpicHoppers vmaven-version-number generated an exception
java.lang.NullPointerException: null
	at com.songoda.epichoppers.storage.serializers.HopperSerializer.serialize(HopperSerializer.java:63) ~[?:?]
	at com.songoda.epichoppers.storage.serializers.HopperSerializer.serialize(HopperSerializer.java:20) ~[?:?]
	at com.google.gson.internal.bind.TreeTypeAdapter.write(TreeTypeAdapter.java:81) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at com.google.gson.Gson.toJson(Gson.java:669) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at com.google.gson.Gson.toJson(Gson.java:648) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at com.google.gson.Gson.toJson(Gson.java:603) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at com.songoda.epichoppers.storage.Database.serialize(Database.java:37) ~[?:?]
	at com.songoda.epichoppers.storage.SQLiteDatabase.save(SQLiteDatabase.java:74) ~[?:?]
	at com.songoda.epichoppers.EpicHoppersPlugin.lambda$saveToFile$2(EpicHoppersPlugin.java:307) ~[?:?]
	at java.util.HashMap.forEach(Unknown Source) ~[?:1.8.0_181]
	at java.util.Collections$UnmodifiableMap.forEach(Unknown Source) ~[?:1.8.0_181]
	at com.songoda.epichoppers.EpicHoppersPlugin.saveToFile(EpicHoppersPlugin.java:307) ~[?:?]
	at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftTask.run(CraftTask.java:81) ~[spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:391) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at net.minecraft.server.v1_13_R2.MinecraftServer.b(MinecraftServer.java:893) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at net.minecraft.server.v1_13_R2.DedicatedServer.b(DedicatedServer.java:417) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:835) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:733) [spigot-1.13.2.jar:git-Spigot-a1f2566-a4c555b]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_181]