BossBars cause client crash on BungeeCord

[BlackBaroness]

Hi!

When I use net.kyori:adventure-platform-bungeecord:4.4.0 to show a bossbar, client just doesn't render it or crashes after a while. Here is an example of code causing this:

val audiences = BungeeAudiences.create(plugin)

for (i in 1..10) {
    // just an example, i make a delay between tries in a real code
    audiences.create(plugin).player(player).showBossBar(
        net.kyori.adventure.bossbar.BossBar.bossBar(
            Component.text("test $i"),
            1f,
            net.kyori.adventure.bossbar.BossBar.Color.RED,
            net.kyori.adventure.bossbar.BossBar.Overlay.NOTCHED_12,
            )
        )
}

Usually I am able to see "test 1" (first bossbar), then I get kicked.

I tried it on a Fabulously Optimized 1.21.8 client and a 1.21.5 + ViaFabricPlus client. Both crashed with the same error.

That's not a client problem since I was able to correctly display bossbars using the "BossBar" packet from BungeeCord API.

Here is an error:

---- Minecraft Network Protocol Error Report ----
// 0xBADF00D

Time: 2025-07-23 23:28:11
Description: Packet handling error

java.lang.NullPointerException: Cannot invoke "net.minecraft.class_345.method_5413(net.minecraft.class_2561)" because the return value of "java.util.Map.get(Object)" is null
	at knot//net.minecraft.class_337$1.method_34102(class_337.java:130)
	at knot//net.minecraft.class_2629$class_5884.method_34106(class_2629.java:237)
	at knot//net.minecraft.class_2629.method_34091(class_2629.java:91)
	at knot//net.minecraft.class_337.method_1795(class_337.java:112)
	at knot//net.minecraft.class_634.method_11078(class_634.java:2032)
	at knot//net.minecraft.class_2629.method_11330(class_2629.java:87)
	at knot//net.minecraft.class_2629.method_65081(class_2629.java:14)
	at knot//net.minecraft.class_2600.method_11072(class_2600.java:27)
	at knot//net.minecraft.class_1255.method_18859(class_1255.java:164)
	at knot//net.minecraft.class_4093.method_18859(class_4093.java:23)
	at knot//net.minecraft.class_1255.method_16075(class_1255.java:138)
	at knot//net.minecraft.class_1255.method_5383(class_1255.java:123)
	at knot//net.minecraft.class_310.method_1523(class_310.java:1318)
	at knot//net.minecraft.class_310.method_1514(class_310.java:947)
	at knot//net.minecraft.client.main.Main.main(Main.java:265)
	at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:480)
	at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74)
	at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)
	at org.prismlauncher.launcher.impl.StandardLauncher.launch(StandardLauncher.java:105)
	at org.prismlauncher.EntryPoint.listen(EntryPoint.java:129)
	at org.prismlauncher.EntryPoint.main(EntryPoint.java:70)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Render thread
Stacktrace:
	at knot//net.minecraft.class_337$1.method_34102(class_337.java:130)
	at knot//net.minecraft.class_2629$class_5884.method_34106(class_2629.java:237)
	at knot//net.minecraft.class_2629.method_34091(class_2629.java:91)
	at knot//net.minecraft.class_337.method_1795(class_337.java:112)
Mixins in Stacktrace: None found

-- Incoming Packet --
Details:
	Type: clientbound/minecraft:boss_event
	Is Terminal: false
	Is Skippable: false
Stacktrace:
	at knot//net.minecraft.class_2600.method_59803(class_2600.java:56)
	at knot//net.minecraft.class_8673.method_60882(class_8673.java:142)
	at knot//net.minecraft.class_8673.method_59807(class_8673.java:121)
	at knot//net.minecraft.class_2600.method_11072(class_2600.java:32)
	at knot//net.minecraft.class_1255.method_18859(class_1255.java:164)
	at knot//net.minecraft.class_4093.method_18859(class_4093.java:23)
	at knot//net.minecraft.class_1255.method_16075(class_1255.java:138)
	at knot//net.minecraft.class_1255.method_5383(class_1255.java:123)
	at knot//net.minecraft.class_310.method_1523(class_310.java:1318)
	at knot//net.minecraft.class_310.method_1514(class_310.java:947)
	at knot//net.minecraft.client.main.Main.main(Main.java:265)
	at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.launch(MinecraftGameProvider.java:480)
	at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:74)
	at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)
	at org.prismlauncher.launcher.impl.StandardLauncher.launch(StandardLauncher.java:105)
	at org.prismlauncher.EntryPoint.listen(EntryPoint.java:129)
	at org.prismlauncher.EntryPoint.main(EntryPoint.java:70)
Mixins in Stacktrace:
	net.minecraft.class_8673:
		net.fabricmc.fabric.mixin.networking.client.ClientCommonNetworkHandlerMixin (fabric-networking-api-v1.client.mixins.json)
		net.fabricmc.fabric.mixin.networking.client.accessor.ClientCommonNetworkHandlerAccessor (fabric-networking-api-v1.client.mixins.json)
		com.aizistral.nochatreports.common.mixins.client.MixinClientPacketListener (mixins/common/nochatreports.mixins.json)
	net.minecraft.class_1255:
		dynamic_fps.impl.mixin.bugfix.BlockableEventLoopMixin (dynamic_fps-common.mixins.json)
	net.minecraft.class_310:
		dev.lambdaurora.lambdynlights.mixin.MinecraftClientMixin (lambdynlights.mixins.json)
		com.aizistral.nochatreports.fabric.mixins.client.MixinMinecraft (mixins/fabric/nochatreports-fabric.mixins.json)
		net.irisshaders.iris.mixin.MixinMinecraft_Images (mixins.iris.json)
		net.fabricmc.fabric.mixin.event.interaction.client.MinecraftClientMixin (fabric-events-interaction-v0.client.mixins.json)
		traben.entity_model_features.mixin.MixinResourceReloadStart (entity_model_features-common.mixins.json)
		traben.entity_texture_features.mixin.reloading.MixinResourceReload (entity_texture_features-common.mixins.json)
		ca.fxco.moreculling.mixin.Minecraft_managersMixin (moreculling.mixins.json)
		dev.isxander.yacl3.mixin.MinecraftMixin (yacl.mixins.json)
		dev.isxander.controlify.mixins.feature.bind.MinecraftMixin (controlify.mixins.json)
		dev.lambdaurora.spruceui.mixin.MinecraftClientMixin (spruceui.mixins.json)
		net.raphimc.immediatelyfast.injection.mixins.core.MixinMinecraftClient (immediatelyfast-common.mixins.json)
		net.fabricmc.fabric.mixin.screen.MinecraftClientMixin (fabric-screen-api-v1.mixins.json)
		me.flashyreese.mods.sodiumextra.mixin.gui.MinecraftClientAccessor (sodium-extra.mixins.json)
		dev.isxander.controlify.mixins.feature.virtualmouse.MinecraftMixin (controlify.mixins.json)
		net.caffeinemc.mods.sodium.mixin.core.MinecraftMixin (sodium-common.mixins.json)
		net.fabricmc.fabric.mixin.event.lifecycle.client.MinecraftClientMixin (fabric-lifecycle-events-v1.client.mixins.json)
		net.irisshaders.iris.mixin.MixinOptions_Entrypoint (mixins.iris.json)
		traben.entity_model_features.mixin.accessor.MinecraftClientAccessor (entity_model_features-common.mixins.json)
		net.fabricmc.fabric.mixin.networking.client.accessor.MinecraftClientAccessor (fabric-networking-api-v1.client.mixins.json)
		me.contaria.fastquit.mixin.MinecraftClientAccessor (fastquit.mixins.json)
		dev.isxander.controlify.mixins.feature.rumble.MinecraftMixin (controlify.mixins.json)
		traben.entity_texture_features.mixin.reloading.MixinMinecraftClient (entity_texture_features-common.mixins.json)
		net.irisshaders.iris.mixin.MixinMinecraft_Keybinds (mixins.iris.json)
		me.flashyreese.mods.sodiumextra.mixin.core.MixinMinecraftClient (sodium-extra.mixins.json)
		ca.fxco.moreculling.mixin.blockstates.Minecraft_loadBlocksMixin (moreculling.mixins.json)
		de.dafuqs.paginatedadvancements.mixin.MinecraftClientMixin (paginatedadvancements.mixins.json)
		me.contaria.fastquit.mixin.MinecraftClientMixin (fastquit.mixins.json)
		net.irisshaders.iris.mixin.MixinMinecraft_PipelineManagement (mixins.iris.json)
		dev.isxander.zoomify.mixins.hooks.MinecraftClientMixin (zoomify.mixins.json)
		dev.isxander.controlify.mixins.feature.input.MinecraftMixin (controlify.mixins.json)
		dev.isxander.controlify.mixins.feature.screenop.MinecraftMixin (controlify.mixins.json)
		net.fabricmc.fabric.mixin.datagen.client.MinecraftClientMixin (fabric-data-generation-api-v1.client.mixins.json)
		net.fabricmc.fabric.mixin.registry.sync.client.MinecraftClientMixin (fabric-registry-sync-v0.client.mixins.json)
		dev.isxander.controlify.mixins.core.MinecraftMixin (controlify.mixins.json)
		opekope2.optigui.mixin.MinecraftClientMixin (optigui.mixins.json)
		ca.fxco.moreculling.mixin.Minecraft_registerReloadListenersMixin (moreculling.fabric.mixins.json)
		dynamic_fps.impl.mixin.MinecraftMixin (dynamic_fps-common.mixins.json)
		org.redlance.dima_dencep.mods.rrls.mixins.MinecraftClientMixin (rrls.mixins.json)
		com.aizistral.nochatreports.common.mixins.client.MixinMinecraft (mixins/common/nochatreports.mixins.json)
		traben.entity_model_features.mixin.MixinResourceReloadEnd (entity_model_features-common.mixins.json)
		me.ramidzkh.fabrishot.mixins.MinecraftClientMixin (mixins.fabrishot.json)
	net.minecraft.client.main.Main:
		dev.kir.cubeswithoutborders.client.mixin.MainMixin (cubes-without-borders.mixins.json)

-- Connection --
Details:
	Protocol: play
	Flow: CLIENTBOUND
	Is Local: false
	Server type: OTHER
	Server brand: BungeeCord (git:BungeeCord-Bootstrap:1.21-R0.4-SNAPSHOT:8e99a4c:1994)