See you later elevator

- Fixed elevator contraptions moving to y=0 when loading in #4830

src/main/java/com/simibubi/create/content/contraptions/elevator/ElevatorColumn.java

@@ -33,6 +33,7 @@ public class ElevatorColumn {
 	protected List<Integer> contacts;
 	protected int targetedYLevel;
 	protected boolean isActive;
+	protected boolean targetAvailable;
 
 	@Nullable
 	public static ElevatorColumn get(LevelAccessor level, ColumnCoords coords) {
@@ -49,6 +50,7 @@ public class ElevatorColumn {
 		this.level = level;
 		this.coords = coords;
 		contacts = new ArrayList<>();
+		targetAvailable = false;
 	}
 
 	public void markDirty() {
@@ -115,6 +117,10 @@ public class ElevatorColumn {
 		targetedYLevel = yLevel;
 	}
 	
+	public boolean isTargetAvailable() {
+		return targetAvailable;
+	}
+
 	public int getTargetedYLevel() {
 		return targetedYLevel;
 	}

src/main/java/com/simibubi/create/content/contraptions/elevator/ElevatorContraption.java

@@ -87,7 +87,9 @@ public class ElevatorContraption extends PulleyContraption {
 		ElevatorColumn column = ElevatorColumn.get(level, coords);
 		if (column == null)
 			return null;
-		int targetedYLevel = column.targetedYLevel;
+		if (!column.isTargetAvailable())
+			return null;
+		int targetedYLevel = column.getTargetedYLevel();
 		if (isTargetUnreachable(targetedYLevel))
 			return null;
 		return targetedYLevel;