[23:14:28 WARN]: [ColorfulMix] Task #326 for ColorfulMix v1.6.2 generated an exception
java.lang.NullPointerException: null
        at org.bukkit.inventory.ItemStack.<init>(ItemStack.java:94) ~[color.jar:git-Spigot-dcd1643-e60fc34]
        at pl.mines.xcraftrayx.ColorfulMix.Game.Arena.getRandomMaterial(Arena.java:253) ~[?:?]
        at pl.mines.xcraftrayx.ColorfulMix.Game.Arena.setMaterialInSection(Arena.java:328) ~[?:?]
        at pl.mines.xcraftrayx.ColorfulMix.Game.Arena.startGame(Arena.java:1019) ~[?:?]
        at pl.mines.xcraftrayx.ColorfulMix.Game.Arena$6.run(Arena.java:996) ~[?:?]
        at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftTask.run(CraftTask.java:76) ~[color.jar:git-Spigot-dcd1643-e60fc34]
        at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:361) [color.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:739) [color.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:406) [color.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:679) [color.jar:git-Spigot-dcd1643-e60fc34]
        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:577) [color.jar:git-Spigot-dcd1643-e60fc34]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_181]