Invalid data below `MaxLayerCell` is not being masked as invalid in output

[xylar]

Fields contain zeros below bathymetry where they should have fill values. Here's an example:

 LayerThickness =
  16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162161, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162161, 
    16.2162162162162, 16.2162162162162, 9.32344193068525, 0, 0, 0, 0, 0, 0,
  16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162161, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162162, 
    16.2162162162162, 16.2162162162162, 16.2162162162162, 16.2162162162161, 
    16.2162162162162, 16.2162162162162, 10.514809877438, 0, 0, 0, 0, 0, 0 ;