Might be malware.

java.lang.NullPointerException: null
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:213) ~[guava-17.0.jar:?]
at com.google.common.io.ByteStreams.copy(ByteStreams.java:170) ~[guava-17.0.jar:?]
at dev.longeh.conquest.utils.image.ImageFolder.load(ImageFolder.java:40) ~[?:?]
at dev.longeh.conquest.utils.image.ImageFolder.<init>(ImageFolder.java:25) ~[?:?]
at dev.longeh.conquest.ConquestPlugin.onEnable(ConquestPlugin.java:24) ~[?:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:321) ~[spigot.jar:git-iSpigot-PaperEdition]
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:322) ~[spigot.jar:git-iSpigot-PaperEdition]
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:389) ~[spigot.jar:git-iSpigot-PaperEdition]
at org.bukkit.craftbukkit.v1_8_R3.CraftServer.loadPlugin(SourceFile:439) ~[spigot.jar:git-iSpigot-PaperEdition]
at org.bukkit.craftbukkit.v1_8_R3.CraftServer.enablePlugins(SourceFile:398) ~[spigot.jar:git-iSpigot-PaperEdition]
at net.minecraft.server.v1_8_R3.MinecraftServer.s(SourceFile:505) ~[spigot.jar:git-iSpigot-PaperEdition]
at net.minecraft.server.v1_8_R3.MinecraftServer.k(SourceFile:430) ~[spigot.jar:git-iSpigot-PaperEdition]
at net.minecraft.server.v1_8_R3.MinecraftServer.a(SourceFile:398) ~[spigot.jar:git-iSpigot-PaperEdition]
at net.minecraft.server.v1_8_R3.DedicatedServer.init(SourceFile:388) ~[spigot.jar:git-iSpigot-PaperEdition]
at net.minecraft.server.v1_8_R3.MinecraftServer.run(SourceFile:728) ~[spigot.jar:git-iSpigot-PaperEdition]
at java.lang.Thread.run(Thread.java:750) [?:1.8.0_342]