Something about grass?

Thread failed: System.DivideByZeroException: Attempted to divide by zero.
at MapMagic.Nodes.MatrixGenerators.GrassOutput200.CreateDetailLayer (Den.Tools.Matrices.Matrix matrix, Den.Tools.Matrices.Matrix biomeMask, System.Single density, System.Int32 randomNum, MapMagic.Products.TileData data, MapMagic.Products.StopToken stop) [0x0000e] in D:\dev\git\NatureManufacture\Assets\MapMagic\Generators\Matrix\Runtime\GrassOut.cs:100
at MapMagic.Nodes.MatrixGenerators.GrassOutput200.Finalize (MapMagic.Products.TileData data, MapMagic.Products.StopToken stop) [0x00090] in D:\dev\git\NatureManufacture\Assets\MapMagic\Generators\Matrix\Runtime\GrassOut.cs:75
at MapMagic.Nodes.Graph.Finalize (MapMagic.Products.TileData data, MapMagic.Products.StopToken stop) [0x0003f] in D:\dev\git\NatureManufacture\Assets\MapMagic\Nodes\Graph.cs:988
at MapMagic.Terrains.TerrainTile.Generate (MapMagic.Nodes.Graph graph, MapMagic.Terrains.TerrainTile tile, MapMagic.Terrains.TerrainTile+DetailLevel det, MapMagic.Products.StopToken stop) [0x0007d] in D:\dev\git\NatureManufacture\Assets\MapMagic\Terrains\TerrainTile.cs:725
at MapMagic.Terrains.TerrainTile+c__DisplayClass50_1.b__0 () [0x00000] in D:\dev\git\NatureManufacture\Assets\MapMagic\Terrains\TerrainTile.cs:677
at Den.Tools.Tasks.ThreadManager.TaskThreadAction (Den.Tools.Tasks.ThreadManager+Task task) [0x00002] in D:\dev\git\NatureManufacture\Assets\MapMagic\Tools\ThreadManager\ThreadManager.cs:138
UnityEngine.Debug:LogError (object)
Den.Tools.Tasks.ThreadManager:TaskThreadAction (Den.Tools.Tasks.ThreadManager/Task) (at Assets/MapMagic/Tools/ThreadManager/ThreadManager.cs:144)
System.Threading.ThreadHelper:ThreadStart ()