Fixed chunk unloading

src/main/java/net/minecraft/server/ChunkProviderServer.java

@@ -206,7 +206,7 @@ public class ChunkProviderServer implements IChunkProvider {
                     chunk.e();
                     this.b(chunk);
                     this.a(chunk);
-                    // this.a.remove(chunkcoordinates); // CraftBukkit
+                    this.a.remove(chunkcoordinates);
                     this.e.remove(chunkcoordinates);
                     this.f.remove(chunk);
                 }

src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -123,6 +123,7 @@ public class CraftWorld implements World {
             provider.a(chunk);
         }
 
+        provider.a.remove(x, z);
         provider.a.remove(x, z);
         provider.e.remove(x, z);
         provider.f.remove(chunk);