Cross referencing this issue from the past: #1207

This is happening still on 1.10.2

java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.8.0_151]
at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.8.0_151]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) [h.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:668) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:387) [ld.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471) [MinecraftServer.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_151]
Caused by: java.lang.NullPointerException
at scala.collection.mutable.ArrayOps$ofRef$.length$extension(ArrayOps.scala:192) ~[ArrayOps$ofRef$.class:?]
at scala.collection.mutable.ArrayOps$ofRef.length(ArrayOps.scala:192) ~[ArrayOps$ofRef.class:?]
at scala.collection.GenSeqLike$class.isDefinedAt(GenSeqLike.scala:72) ~[GenSeqLike$class.class:?]
at scala.collection.mutable.ArrayOps$ofRef.isDefinedAt(ArrayOps.scala:186) ~[ArrayOps$ofRef.class:?]
at mrtjp.core.inventory.TInventory$$anonfun$loadInv$1.apply$mcVI$sp(invtraits.scala:89) ~[TInventory$$anonfun$loadInv$1.class:?]
at scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:160) ~[Range.class:?]
at mrtjp.core.inventory.TInventory$class.loadInv(invtraits.scala:84) ~[TInventory$class.class:?]
at mrtjp.projectred.exploration.BagInventory.loadInv(items.scala:114) ~[BagInventory.class:?]
at mrtjp.core.inventory.TInventory$class.loadInv(invtraits.scala:80) ~[TInventory$class.class:?]
at mrtjp.projectred.exploration.BagInventory.loadInv(items.scala:114) ~[BagInventory.class:?]
at mrtjp.projectred.exploration.BagInventory.loadInventory(items.scala:125) ~[BagInventory.class:?]
at mrtjp.projectred.exploration.BagInventory.(items.scala:116) ~[BagInventory.class:?]
at mrtjp.projectred.exploration.ItemBackpack$.createContainer(items.scala:77) ~[ItemBackpack$.class:?]
at mrtjp.projectred.exploration.ItemBackpack.openGui(items.scala:54) ~[ItemBackpack.class:?]
at mrtjp.projectred.exploration.ItemBackpack.func_77659_a(items.scala:48) ~[ItemBackpack.class:?]
at net.minecraft.item.ItemStack.func_77957_a(ItemStack.java:163) ~[adz.class:?]
at net.minecraft.server.management.PlayerInteractionManager.func_187250_a(PlayerInteractionManager.java:365) ~[lv.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_147346_a(NetHandlerPlayServer.java:710) ~[me.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItem.func_148833_a(SourceFile:32) ~[jk.class:?]
at net.minecraft.network.play.client.CPacketPlayerTryUseItem.func_148833_a(SourceFile:9) ~[jk.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[fl$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_151]
at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_151]
at net.minecraft.util.Util.func_181617_a(SourceFile:45) ~[h.class:?]
... 5 more
[18:45:06] [Netty Server IO #3/ERROR] [FML]: NetworkDispatcher exception
java.io.IOException: An existing connection was forcibly closed by the remote host
at sun.nio.ch.SocketDispatcher.read0(Native Method) ~[?:1.8.0_151]
at sun.nio.ch.SocketDispatcher.read(Unknown Source) ~[?:1.8.0_151]
at sun.nio.ch.IOUtil.readIntoNativeBuffer(Unknown Source) ~[?:1.8.0_151]
at sun.nio.ch.IOUtil.read(Unknown Source) ~[?:1.8.0_151]
at sun.nio.ch.SocketChannelImpl.read(Unknown Source) ~[?:1.8.0_151]
at io.netty.buffer.UnpooledUnsafeDirectByteBuf.setBytes(UnpooledUnsafeDirectByteBuf.java:446) ~[UnpooledUnsafeDirectByteBuf.class:?]
at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:881) ~[AbstractByteBuf.class:?]
at io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:225) ~[NioSocketChannel.class:?]
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:119) [AbstractNioByteChannel$NioByteUnsafe.class:?]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511) [NioEventLoop.class:?]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468) [NioEventLoop.class:?]
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382) [NioEventLoop.class:?]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354) [NioEventLoop.class:?]
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) [SingleThreadEventExecutor$2.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_151]

Seems to be fixed in 5417878

It isn't fixed as I've also been getting this bug for quite sometime. I apologize if I'm doing something wrong but I'm pretty sure I've covered user error. I didn't think making another issue post was necessary but I will if this doesn't get addressed here further as it's been outstanding for quite some time.

This happens still with 1.10.2, MrTJPCore 2.0.1.20 and Project Red 4.8.4.49, which are the only versions available on the CurseForge and as far as I know, and are marked as release versions. I'm uncertain if using Twitch to set up mod packs could be the cause but haven't found any evidence of that yet.

The steps I've taken to reproduce are installing a fresh Forge 12.18.3.2511 profile by way of the Twitch client. Then only installing the necessary .jar files for Project red to work. I go into creative mode to test. I pull a backpack from the creative inventory. I open it up and place an item inside. When I try to open the pack, the game crashes. This is the log that I get from this procedure:

https://pastebin.com/vZwgi7ma

Duplicate of #1216