net.minecraft.server.v1_15_R1.ReportedException: Loading entity NBT
        at net.minecraft.server.v1_15_R1.Entity.f(Entity.java:1703) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.EntityTypes.lambda$101(EntityTypes.java:301) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.SystemUtils.a(SourceFile:341) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.EntityTypes.a(EntityTypes.java:298) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.EntityTypes.b(EntityTypes.java:342) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.EntityTypes.a(EntityTypes.java:323) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.CommandSummon.a(CommandSummon.java:38) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.CommandSummon.lambda$1(CommandSummon.java:18) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:262) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:176) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.CommandDispatcher.a(CommandDispatcher.java:179) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at org.bukkit.craftbukkit.v1_15_R1.command.VanillaCommandWrapper.execute(VanillaCommandWrapper.java:45) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:149) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at org.bukkit.craftbukkit.v1_15_R1.CraftServer.dispatchCommand(CraftServer.java:711) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.PlayerConnection.handleCommand(PlayerConnection.java:1657) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.PlayerConnection.a(PlayerConnection.java:1497) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.PacketPlayInChat.a(PacketPlayInChat.java:47) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.PacketPlayInChat.a(PacketPlayInChat.java:1) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.PlayerConnectionUtils.lambda$0(PlayerConnectionUtils.java:19) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.TickTask.run(SourceFile:18) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeTask(SourceFile:144) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.IAsyncTaskHandlerReentrant.executeTask(SourceFile:23) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeNext(SourceFile:118) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.MinecraftServer.aZ(MinecraftServer.java:917) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.MinecraftServer.executeNext(MinecraftServer.java:910) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.IAsyncTaskHandler.awaitTasks(SourceFile:127) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.MinecraftServer.sleepForTick(MinecraftServer.java:894) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:827) [spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at java.lang.Thread.run(Thread.java:830) [?:?]
Caused by: java.lang.IllegalArgumentException: Cannot drop air
        at com.google.common.base.Preconditions.checkArgument(Preconditions.java:122) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.EntityItem.setItemStack(EntityItem.java:397) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.EntityItem.a(EntityItem.java:307) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        at net.minecraft.server.v1_15_R1.Entity.f(Entity.java:1648) ~[spigot-1.15.1.jar:git-Spigot-492a779-b98e2de]
        ... 28 more