Migrated from: https://dev.bukkit.org/projects/shopkeepers/issues/344

Originally posted by Telbaru (Oct 4, 2015):

Everytime you sell Player heads with the Villagers and the player from this head change his name, the plugin deletes the complete save.yml because the plugin didn't find the playerheads name.Running System: - CraftBukkit version git-Spigot-fdc1440-53fac9f (MC: 1.8.8) (Implementing API version 1.8.8-R0.1-SNAPSHOT)
                          - Shopkeepers v1.63Error:
[17:32:11] [Craft Scheduler Thread - 299/WARN]: Exception in thread "Craft Scheduler Thread - 299"
[17:32:11] [Craft Scheduler Thread - 299/WARN]: org.apache.commons.lang.UnhandledException: Plugin Shopkeepers v1.63 generated an exception while executing task 81576
    at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException: null value in entry: skull-owner=null
    at com.google.common.collect.CollectPreconditions.checkEntryNotNull(CollectPreconditions.java:33)
    at com.google.common.collect.ImmutableMap.entryOf(ImmutableMap.java:135)
    at com.google.common.collect.ImmutableMap$Builder.put(ImmutableMap.java:206)
    at org.bukkit.craftbukkit.v1_8_R3.inventory.CraftMetaSkull.serialize(CraftMetaSkull.java:173)
    at org.bukkit.craftbukkit.v1_8_R3.inventory.CraftMetaItem.serialize(CraftMetaItem.java:850)
    at org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSerializable.representData(YamlRepresenter.java:33)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:156)
    at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:304)
    at org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSerializable.representData(YamlRepresenter.java:35)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:156)
    at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:304)
    at org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSection.representData(YamlRepresenter.java:23)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:156)
    at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:304)
    at org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSection.representData(YamlRepresenter.java:23)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:156)
    at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:304)
    at org.bukkit.configuration.file.YamlRepresenter$RepresentConfigurationSection.representData(YamlRepresenter.java:23)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representMapping(BaseRepresenter.java:156)
    at org.yaml.snakeyaml.representer.SafeRepresenter$RepresentMap.representData(SafeRepresenter.java:304)
    at org.yaml.snakeyaml.representer.BaseRepresenter.representData(BaseRepresenter.java:94)
    at org.yaml.snakeyaml.representer.BaseRepresenter.represent(BaseRepresenter.java:64)
    at org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:242)
    at org.yaml.snakeyaml.Yaml.dumpAll(Yaml.java:206)
    at org.yaml.snakeyaml.Yaml.dump(Yaml.java:181)
    at org.bukkit.configuration.file.YamlConfiguration.saveToString(YamlConfiguration.java:40)
    at com.nisovin.shopkeepers.ShopkeepersPlugin.saveDataToFile(ShopkeepersPlugin.java:1390)
    at com.nisovin.shopkeepers.ShopkeepersPlugin.access$1200(ShopkeepersPlugin.java:62)
    at com.nisovin.shopkeepers.ShopkeepersPlugin$11.run(ShopkeepersPlugin.java:1300)
    at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftTask.run(CraftTask.java:71)
    at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
    ... 3 more

Originally commented by blablubbabc (Oct 4, 2015):

Duplicate of this closed ticket.
This is something the spigot team has to fix. I created a spigot ticket for it here.

Originally closed by blablubbabc (Oct 4, 2015)