Synchronized tile modification with updating

core/assets/version.properties

@@ -1,7 +1,7 @@
 #Autogenerated file. Do not modify.
-#Sat Feb 17 13:59:09 EST 2018
+#Sat Feb 17 14:39:13 EST 2018
 version=beta
 androidBuildCode=235
 name=Mindustry
 code=3.3
-build=23
+build=custom build

core/src/io/anuke/mindustry/entities/TileEntity.java

@@ -106,6 +106,7 @@ public class TileEntity extends Entity{
 	
 	@Override
 	public void update(){
+		synchronized (tile) {
 			if (health != 0 && health < tile.block().health && !(tile.block() instanceof Wall) &&
 					Mathf.chance(0.009f * Timers.delta() * (1f - health / tile.block().health))) {
 
@@ -118,6 +119,7 @@ public class TileEntity extends Entity{
 
 			tile.block().update(tile);
 		}
+	}
 	
 	public int totalItems(){
 		int sum = 0;

core/src/io/anuke/mindustry/world/Tile.java

@@ -260,6 +260,7 @@ public class Tile{
 	}
 	
 	public void changed(){
+		synchronized (this) {
 			if (entity != null) {
 				entity.remove();
 				entity = null;
@@ -273,6 +274,7 @@ public class Tile{
 
 			updateOcclusion();
 		}
+	}
 	
 	@Override
 	public String toString(){

core/src/io/anuke/mindustry/world/blocks/types/distribution/Conveyor.java

@@ -143,7 +143,6 @@ public class Conveyor extends Block{
 
 	@Override
 	public boolean acceptItem(Item item, Tile tile, Tile source){
-		if(tile.entity == null) return false;
 		int direction = source == null ? 0 : Math.abs(source.relativeTo(tile.x, tile.y) - tile.getRotation());
 		float minitem = tile.<ConveyorEntity>entity().minitem;
 		return (((direction == 0) && minitem > 0.05f) ||