I am getting the following error when trying to register a renderer for my new entity.

[m[1;31m[21:10:56] [modloading-worker-2/ERROR] [ne.mi.fm.ja.FMLModContainer/]: Exception caught during firing event: null
	Index: 1
	Listeners:
		0: NORMAL
		1: net.minecraftforge.eventbus.EventBus$$Lambda$2065/1415390560@32f53aa7
java.lang.NullPointerException
	at java.util.concurrent.ConcurrentHashMap.putVal(Unknown Source)
	at java.util.concurrent.ConcurrentHashMap.put(Unknown Source)
	at net.minecraftforge.fml.client.registry.RenderingRegistry.registerEntityRenderingHandler(RenderingRegistry.java:44)
	at com.blockvader.reforging.client.ClientProxy.registerEntityModels(ClientProxy.java:23)
	at com.blockvader.reforging.Reforging.clientSetup(Reforging.java:36)
	at net.minecraftforge.eventbus.EventBus.doCastFilter(EventBus.java:212)
	at net.minecraftforge.eventbus.EventBus.lambda$addListener$11(EventBus.java:204)
	at net.minecraftforge.eventbus.EventBus.post(EventBus.java:258)
	at net.minecraftforge.fml.javafmlmod.FMLModContainer.fireEvent(FMLModContainer.java:106)
	at java.util.function.Consumer.lambda$andThen$0(Unknown Source)
	at java.util.function.Consumer.lambda$andThen$0(Unknown Source)
	at net.minecraftforge.fml.ModContainer.transitionState(ModContainer.java:112)
	at net.minecraftforge.fml.ModList.lambda$null$10(ModList.java:135)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(Unknown Source)
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(Unknown Source)
	at java.util.stream.AbstractPipeline.copyInto(Unknown Source)
	at java.util.stream.ForEachOps$ForEachTask.compute(Unknown Source)
	at java.util.concurrent.CountedCompleter.exec(Unknown Source)
	at java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(Unknown Source)
	at java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
	at java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)

[m[1;31m[21:10:56] [modloading-worker-2/ERROR] [ne.mi.fm.ja.FMLModContainer/LOADING]: Caught exception during event FMLClientSetupEvent dispatch for modid reforging
java.lang.NullPointerException: null
	at java.util.concurrent.ConcurrentHashMap.putVal(Unknown Source) ~[?:1.8.0_171] {}
	at java.util.concurrent.ConcurrentHashMap.put(Unknown Source) ~[?:1.8.0_171] {}
	at net.minecraftforge.fml.client.registry.RenderingRegistry.registerEntityRenderingHandler(RenderingRegistry.java:44) ~[forge-1.15.2-31.2.0_mapped_snapshot_20200514-1.15.1-recomp.jar:?] {re:classloading}
	at com.blockvader.reforging.client.ClientProxy.registerEntityModels(ClientProxy.java:23) ~[main/:?] {re:classloading}
	at com.blockvader.reforging.Reforging.clientSetup(Reforging.java:36) ~[main/:?] {re:classloading}
	at net.minecraftforge.eventbus.EventBus.doCastFilter(EventBus.java:212) ~[eventbus-2.2.0-service.jar:?] {}
	at net.minecraftforge.eventbus.EventBus.lambda$addListener$11(EventBus.java:204) ~[eventbus-2.2.0-service.jar:?] {}
	at net.minecraftforge.eventbus.EventBus.post(EventBus.java:258) ~[eventbus-2.2.0-service.jar:?] {}
	at net.minecraftforge.fml.javafmlmod.FMLModContainer.fireEvent(FMLModContainer.java:106) ~[?:31.2] {re:classloading}
	at java.util.function.Consumer.lambda$andThen$0(Unknown Source) ~[?:1.8.0_171] {}
	at java.util.function.Consumer.lambda$andThen$0(Unknown Source) ~[?:1.8.0_171] {}
	at net.minecraftforge.fml.ModContainer.transitionState(ModContainer.java:112) ~[?:?] {re:classloading}
	at net.minecraftforge.fml.ModList.lambda$null$10(ModList.java:135) ~[?:?] {re:classloading}
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(Unknown Source) [?:1.8.0_171] {}
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(Unknown Source) [?:1.8.0_171] {}
	at java.util.stream.AbstractPipeline.copyInto(Unknown Source) [?:1.8.0_171] {}
	at java.util.stream.ForEachOps$ForEachTask.compute(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.CountedCompleter.exec(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.ForkJoinTask.doExec(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.ForkJoinPool.runWorker(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source) [?:1.8.0_171] {}
[m[1;31m[21:10:56] [Server-Worker-2/FATAL] [ne.mi.fm.ModLoader/LOADING]: Failed to complete lifecycle event SIDED_SETUP, 1 errors found
[m[1;31m[21:10:56] [Server-Worker-2/FATAL] [ne.mi.ev.EventBus/EVENTBUS]: EventBus 0 shutting down - future events will not be posted.
java.lang.Exception: stacktrace
	at net.minecraftforge.eventbus.EventBus.shutdown(EventBus.java:278) ~[eventbus-2.2.0-service.jar:?] {}
	at net.minecraftforge.fml.client.ClientModLoader.lambda$createRunnableWithCatch$5(ClientModLoader.java:115) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
	at net.minecraftforge.fml.client.ClientModLoader.startModLoading(ClientModLoader.java:123) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
	at net.minecraftforge.fml.client.ClientModLoader.lambda$onreload$3(ClientModLoader.java:105) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
	at net.minecraftforge.fml.client.ClientModLoader.lambda$createRunnableWithCatch$5(ClientModLoader.java:113) ~[?:?] {re:classloading,pl:runtimedistcleaner:A}
	at java.util.concurrent.CompletableFuture$AsyncRun.run(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.CompletableFuture$AsyncRun.exec(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.ForkJoinTask.doExec(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.ForkJoinPool.runWorker(Unknown Source) [?:1.8.0_171] {}
	at java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source) [?:1.8.0_171] {}

Renderer class

public class ShockwaveRenderer extends EntityRenderer<ShockwaveEntity>{

	public ShockwaveRenderer(EntityRendererManager renderManager)
	{
		super(renderManager);
	}

	@Override
	public ResourceLocation getEntityTexture(@Nonnull ShockwaveEntity entity) 
	{
		return null;
	}
}

Registering renderer

public static void registerEntityModels()
{
	RenderingRegistry.registerEntityRenderingHandler(ModEntities.SHOCKWAVE, ShockwaveRenderer::new);
}

I have registered entity renderer this way in the past and it worked without error. I don't understand what is the problem now.

41 minutes ago, fcelon said:

ModEntities.SHOCKWAVE

This is probably null. Likely because you're calling this code too early.

also iirc returning null in

getEntityTexture

is not allowed (will crash)

Thakns you, ModEntities.SHOCKWAVE was indeed null. And getEntityTexture returning null doesn't seen to crash.