craftbukkit/nms-patches/net/minecraft/server/level/ChunkMapDistance.patch

--- a/net/minecraft/server/level/ChunkMapDistance.java
+++ b/net/minecraft/server/level/ChunkMapDistance.java
@@ -77,6 +77,11 @@
         }
 
         if (!this.chunksToUpdateFutures.isEmpty()) {
+            // CraftBukkit start - SPIGOT-7780: Call chunk unload events before updateHighestAllowedStatus
+            for (PlayerChunk playerchunk : this.chunksToUpdateFutures) {
+                playerchunk.callEventIfUnloading(playerchunkmap);
+            }
+            // CraftBukkit end
             for (PlayerChunk playerchunk : this.chunksToUpdateFutures) {
                 playerchunk.updateHighestAllowedStatus(playerchunkmap);
             }
@@ -137,6 +142,7 @@
         ChunkCoordIntPair chunkcoordintpair = sectionposition.chunk();
         long i = chunkcoordintpair.toLong();
         ObjectSet<EntityPlayer> objectset = (ObjectSet) this.playersPerChunk.get(i);
+        if (objectset == null) return; // CraftBukkit - SPIGOT-6208
 
         objectset.remove(entityplayer);
         if (objectset.isEmpty()) {