Prevent visual plastanium conveyor glitch when disabled (#4101)

core/src/mindustry/world/blocks/distribution/StackConveyor.java

@@ -179,14 +179,18 @@ public class StackConveyor extends Block implements Autotiler{
             }
         }
 
+        @Override
+        public float efficiency(){
+            return 1f;
+        }
+
         @Override
         public void updateTile(){
             // reel in crater
             if(cooldown > 0f) cooldown = Mathf.clamp(cooldown - speed * edelta(), 0f, recharge);
 
-            if(link == -1){
-                return;
-            }
+            // indicates empty state
+            if(link == -1) return;
 
             // crater needs to be centered
             if(cooldown > 0f) return;
@@ -196,6 +200,9 @@ public class StackConveyor extends Block implements Autotiler{
                 lastItem = items.first();
             }
 
+            // do not continue if disabled, will still allow one to be reeled in to prevent visual stacking
+            if(!enabled) return;
+
             if(state == stateUnload){ //unload
                 while(lastItem != null && (!splitOut ? moveForward(lastItem) : dump(lastItem))){
                     if(items.empty()) poofOut();