Properly offset marker by y1.8 again

src/main/java/com/technicjelle/bluemapofflineplayermarkers/core/markerhandler/BlueMapMarkerHandler.java

@@ -32,7 +32,7 @@ public void add(Player player, BlueMapAPI api) {
 		if (position == null) return;
 
 		// Add 1.8 to y to place the marker at the head-position of the player, like BlueMap does with its player-markers
-		position.add(0, 1.8, 0);
+		position = position.add(0, 1.8, 0);
 
 		// Create marker-template
 		POIMarker.Builder markerBuilder = POIMarker.builder()