crash when attempting to sync inventory with unsupported items

[vfreex]

Issue Description:

I have 2 sponge servers. One is moded, while the other is original.
If a player keeps items extended by mods then switch to the original server, InvSync will crash and out-of-sync.

• Minecraft: 1.11.2
• InvSync: 0.6.14
• Sponge: 1.10.2-2281-5.2.0-BETA-2394
• Other related mods:
  forge-1.10.2-12.18.3.2281
  ThermalExpansion-1.10.2-5.1.3.4

Your most recent log or stack trace file where the issue was present:

[18:18:24 ERROR] [Sponge]: The Scheduler tried to run the task invsync-S-2 owned by Plugin{id=invsync, name=Inventory Sync, version=0.6.14, description=This plugin synchronizes the player inventory with a database, url=https://github.com/BrainStone/InvSync, authors=[The_BrainStone], source=mods/InvSync-0.6.14.jar}, but an error occured.
java.util.NoSuchElementException: No value present
        at java.util.Optional.get(Optional.java:135) ~[?:1.8.0_131]
        at org.spongepowered.common.item.inventory.SpongeItemStackBuilder.fromContainer(SpongeItemStackBuilder.java:168) ~[SpongeItemStackBuilder.class:1.10.2-5.2.0-BETA-387]
        at world.jnc.invsync.util.serializer.InventorySerializer.deserializeItemStack(InventorySerializer.java:79) ~[InventorySerializer.class:0.6.14]
        at world.jnc.invsync.util.serializer.InventorySerializer.deserializeInventory(InventorySerializer.java:56) ~[InventorySerializer.class:0.6.14]
        at world.jnc.invsync.util.serializer.PlayerSerializer.deserializePlayer(PlayerSerializer.java:133) ~[PlayerSerializer.class:0.6.14]
        at world.jnc.invsync.event.PlayerEvents.loadPlayer(PlayerEvents.java:154) ~[PlayerEvents.class:0.6.14]
        at world.jnc.invsync.event.PlayerEvents.access$200(PlayerEvents.java:33) ~[PlayerEvents.class:0.6.14]
        at world.jnc.invsync.event.PlayerEvents$WaitingForPreviousServerToFinish.accept(PlayerEvents.java:194) ~[PlayerEvents$WaitingForPreviousServerToFinish.class:0.6.14]
        at world.jnc.invsync.event.PlayerEvents$WaitingForPreviousServerToFinish.accept(PlayerEvents.java:166) ~[PlayerEvents$WaitingForPreviousServerToFinish.class:0.6.14]
        at org.spongepowered.common.scheduler.SchedulerBase.lambda$startTask$0(SchedulerBase.java:183) ~[SchedulerBase.class:1.10.2-5.2.0-BETA-387]
        at org.spongepowered.common.scheduler.SyncScheduler.executeTaskRunnable(SyncScheduler.java:81) ~[SyncScheduler.class:1.10.2-5.2.0-BETA-387]
        at org.spongepowered.common.scheduler.SchedulerBase.startTask(SchedulerBase.java:179) ~[SchedulerBase.class:1.10.2-5.2.0-BETA-387]
        at org.spongepowered.common.scheduler.SchedulerBase.processTask(SchedulerBase.java:165) ~[SchedulerBase.class:1.10.2-5.2.0-BETA-387]
        at java.util.concurrent.ConcurrentHashMap$ValuesView.forEach(ConcurrentHashMap.java:4707) [?:1.8.0_131]
        at org.spongepowered.common.scheduler.SchedulerBase.runTick(SchedulerBase.java:108) [SchedulerBase.class:1.10.2-5.2.0-BETA-387]
        at org.spongepowered.common.scheduler.SyncScheduler.tick(SyncScheduler.java:51) [SyncScheduler.class:1.10.2-5.2.0-BETA-387]
        at org.spongepowered.common.scheduler.SpongeScheduler.tickSyncScheduler(SpongeScheduler.java:191) [SpongeScheduler.class:1.10.2-5.2.0-BETA-387]
        at net.minecraft.server.dedicated.DedicatedServer.handler$onTick$zob000(SourceFile:1253) [ld.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(SourceFile:340) [ld.class:?]
        at net.minecraft.server.MinecraftServer.func_71217_p(SourceFile:554) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(SourceFile:458) [MinecraftServer.class:?]
        at java.lang.Thread.run(Thread.java:748) [?:1.8.0_131]

Is there any possibility to avoid this kind of crash and block unsupported items?

[BrainStone]

I'm not sure what I could do about it. Sure I could catch the exception. But that would mean that all unsupported items would be deleted.
The plugin is not designed to be used on different modpacks

[vfreex]

Is there a placeholder for unsupported items?
I know sync items between different modpacks or Minecraft versions is not easy. At the present time I only uses Ender chests to sync between those different kinds of servers, so deleting unsupported items may be a feasible choice. Maybe adding an option to let users make the decision whether to delete unsupported items?

[BrainStone]

Well, ok. I'll make sure that unsupported items will just get deleted. I can't really make that an option tbh

[vfreex]

Thanks for your quick response.
Just another idea: When fail to add an item, move it to a temporary collection rather than delete it. So we can move all items in the temporary collection back when the user is leaving the world.

[BrainStone]

Oh boy. That is more complicated than you imagine. Alone storing it is a hassle. Let alone all the corner cases like the former slot is now occupied, your the container doesn't have any free slots...

[BrainStone]

You can follow #19