From df371c1b69b3c8e751680b4429e0a0e7bab664d9 Mon Sep 17 00:00:00 2001
From: md_5 <git@md-5.net>
Date: Fri, 31 Jan 2020 08:36:59 +1100
Subject: [PATCH] SPIGOT-5554: Clear error message when BossBar is used for not
 fully joined players

---
 src/main/java/org/bukkit/craftbukkit/boss/CraftBossBar.java | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/main/java/org/bukkit/craftbukkit/boss/CraftBossBar.java b/src/main/java/org/bukkit/craftbukkit/boss/CraftBossBar.java
index d1033d73d4..4a7e5fde00 100644
--- a/src/main/java/org/bukkit/craftbukkit/boss/CraftBossBar.java
+++ b/src/main/java/org/bukkit/craftbukkit/boss/CraftBossBar.java
@@ -166,11 +166,16 @@ public class CraftBossBar implements BossBar {
 
     @Override
     public void addPlayer(Player player) {
+        Preconditions.checkArgument(player != null, "player == null");
+        Preconditions.checkArgument(((CraftPlayer) player).getHandle().playerConnection != null, "player is not fully connected (wait for PlayerJoinEvent)");
+
         handle.addPlayer(((CraftPlayer) player).getHandle());
     }
 
     @Override
     public void removePlayer(Player player) {
+        Preconditions.checkArgument(player != null, "player == null");
+
         handle.removePlayer(((CraftPlayer) player).getHandle());
     }