[Server thread/ERROR]: Error occurred while disabling VirtualBag v3.0 (Is it up to date?)
java.lang.NullPointerException: null value in entry: skull-owner=null
	at com.google.common.collect.CollectPreconditions.checkEntryNotNull(CollectPreconditions.java:33) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at com.google.common.collect.ImmutableMap.entryOf(ImmutableMap.java:135) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at com.google.common.collect.ImmutableMap$Builder.put(ImmutableMap.java:206) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.craftbukkit.v1_8_R3.inventory.CraftMetaSkull.serialize(CraftMetaSkull.java:173) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.craftbukkit.v1_8_R3.inventory.CraftMetaItem.serialize(CraftMetaItem.java:850) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSerializable.representData(YamlRepresenter.java:33) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:156) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:304) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSerializable.representData(YamlRepresenter.java:35) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representSequence(BaseRepresenter.java:133) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentArray.representData(SafeRepresenter.java:202) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:156) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:304) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSection.representData(YamlRepresenter.java:23) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:156) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:304) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.representer.BaseRepresenter.represent(BaseRepresenter.java:64) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:242) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:206) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.yaml.snakeyaml.Yaml.dump(Yaml.java:181) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.configuration.file.YamlConfiguration.saveToString(YamlConfiguration.java:40) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.configuration.file.FileConfiguration.save(FileConfiguration.java:103) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at com.cracksn0w.virtualbag.utils.ConfigurationManager.saveConfiguration(ConfigurationManager.java:51) ~[?:?]
	at com.cracksn0w.virtualbag.VirtualBagManager.saveVirtualBags(VirtualBagManager.java:76) ~[?:?]
	at com.cracksn0w.virtualbag.VirtualBagPlugin.onDisable(VirtualBagPlugin.java:46) ~[?:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:323) ~[spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:364) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.plugin.SimplePluginManager.disablePlugin(SimplePluginManager.java:424) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.plugin.SimplePluginManager.disablePlugins(SimplePluginManager.java:417) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.bukkit.craftbukkit.v1_8_R3.CraftServer.disablePlugins(CraftServer.java:336) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at net.minecraft.server.v1_8_R3.MinecraftServer.stop(MinecraftServer.java:460) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.spigotmc.RestartCommand.restart(RestartCommand.java:81) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.spigotmc.RestartCommand.restart(RestartCommand.java:40) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at org.spigotmc.RestartCommand$1.run(RestartCommand.java:31) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at net.minecraft.server.v1_8_R3.MinecraftServer.B(MinecraftServer.java:729) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at net.minecraft.server.v1_8_R3.DedicatedServer.B(DedicatedServer.java:374) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at net.minecraft.server.v1_8_R3.MinecraftServer.A(MinecraftServer.java:654) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:557) [spigot_1.8.8_20.10.jar:git-Spigot-5f38d38-18fbb24]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_60]