Applied Energistics 2

Describe the bug
Upon hosting the server it won't go futher than it saying that the server crashed because of Applied Energistics 2.

To Reproduce
Just hosting the server.

Expected behavior
Hosting the server normal like for the past week or two.

Additional context
https://cdn.discordapp.com/attachments/603633700772773889/603647018702995456/latest.log
No actual crashlogs are to be found with this problem.
Environment
The Classic Pack via the TechnicLauncher.
Thaumic Additions: reconstructed, Last updated Jun 22, 2019

Minecraft Version: 1.12.1
AE2 Version: Not sure, The version before the 23-7-19 Version, don't know where to check where the version is listed.
Forge Version: Not using Forge, Using Technic Launcher and added to the Classic Pack (tekkit)

Sponge isn't supported. Try if reproducible with Vanilla ForgeServer.

Additional Context:
Stacktrace:

Caused by: java.lang.NullPointerException
	at appeng.core.AppEng.serverStopped(AppEng.java:271)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:624)
	at sun.reflect.GeneratedMethodAccessor10.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91)
	at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150)
	at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76)
	at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399)
	at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71)
	at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116)
	at com.google.common.eventbus.EventBus.post(EventBus.java:217)
	at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:219)
	at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:197)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91)
	at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150)
	at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76)
	at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399)
	at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71)
	at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116)
	at com.google.common.eventbus.EventBus.post(EventBus.java:217)
	at net.minecraftforge.fml.common.LoadController.redirect$onPost$zza000(LoadController.java:560)
	at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:136)
	at net.minecraftforge.fml.common.Loader.serverStopped(Loader.java:847)
	at net.minecraftforge.fml.common.FMLCommonHandler.handleServerStopped(FMLCommonHandler.java:508)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:587)
	at java.lang.Thread.run(Unknown Source)

Line in Question:

Applied-Energistics-2/src/main/java/appeng/core/AppEng.java

Line 271 in c483bd1

WorldData.instance().onServerStoppped();

this instance is per definition Nullable

Applied-Energistics-2/src/main/java/appeng/core/worlddata/WorldData.java

Lines 59 to 60 in c483bd1

    
           @Nullable 
        
           private static IWorldData instance;

The method states it never returns null

Applied-Energistics-2/src/main/java/appeng/core/worlddata/WorldData.java

Lines 111 to 117 in c483bd1

    
           @Deprecated 
        
           @Nonnull 
        
           public static IWorldData instance() 
        
           { 
        
           	return instance; 
        
           }

Contradicts! Worstcase should assumed: Therefore a Null check in AppEng.java should be performed

The thing is, how is it ending up in ServerStopped in the first place? I can understand the stacktrace for the NPE, but when that trace is logged, the server is already stopping. It doesn't seem to be the cause of the crash, but a side-effect.

Sponge wasn't supported since day one of the server host and hasn't caused any problems with it. I am not really able to follow you but if you could tell me what to do for you to check something out I'll surely want to help if possible.

@yueh

Need to wait @yueh to look at it. (The addtional context I have provided is meant for him)
I have looked into the code and some information in it contradicts each other. Additionally, the call the causes the issue is already marked as deprecated and should no longer be used anywhere.
(The many edits were caused by backtracking all the calls)

We do not support anything like Sponge or Bukkit officially. Only a standard forge environment.

Should you be able to reproduce it without it and in a new environment and save, please update the issue accordingly and we will reopen it.

	@Deprecated
	@Nonnull
	public static IWorldData instance()
	{
	return instance;
	}

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