Don't crash if player is attempted to be removed from untracked chunk.

I suspect it deals with teleporting as it uses players current x/y/z

Fixes #2803

Spigot-Server-Patches/0484-Don-t-crash-if-player-is-attempted-to-be-removed-fro.patch

@@ -0,0 +1,23 @@
+From 86e26e7c235ffbd1dc52242b42c40ff55bef6b4c Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Sat, 18 Apr 2020 15:59:41 -0400
+Subject: [PATCH] Don't crash if player is attempted to be removed from
+ untracked chunk.
+
+I suspect it deals with teleporting as it uses players current x/y/z
+
+diff --git a/src/main/java/net/minecraft/server/ChunkMapDistance.java b/src/main/java/net/minecraft/server/ChunkMapDistance.java
+index 0244768f7..279c7a85f 100644
+--- a/src/main/java/net/minecraft/server/ChunkMapDistance.java
++++ b/src/main/java/net/minecraft/server/ChunkMapDistance.java
+@@ -226,6 +226,7 @@ public abstract class ChunkMapDistance {
+     public void b(SectionPosition sectionposition, EntityPlayer entityplayer) {
+         long i = sectionposition.u().pair();
+         ObjectSet<EntityPlayer> objectset = (ObjectSet) this.c.get(i);
++        if (objectset == null) return; // Paper - mitigate weird state mismatch that this chunk isn't tracked.
+ 
+         objectset.remove(entityplayer);
+         if (objectset.isEmpty()) {
+-- 
+2.25.1
+

paper

@@ -50,6 +50,17 @@ case "$1" in
         scripts/build.sh "$basedir" "--jar" || exit 1
     ) || failed=1
     ;;
+    "b" | "build")
+    (
+        set -e
+        cd "$basedir"
+        scripts/build.sh "$basedir" || exit 1
+        (cd Paper-API ; mvn clean install) || exit 1
+        (cd Paper-Server ; mvn clean package) || exit 1
+        echo "Paper jar successfully built"
+        ls -la Paper-Server/target/paper*.jar
+    ) || failed=1
+    ;;
     "make")
     (
         if [[ "$2" = "bacon" ]] ; then