[Need Help] TerrainFractalGrid Get Height?

Hey Everyone!
I working now a long time with the SDK and solved the most of my Bugs.
But the last Days making me much sad…
I want to place my random generated Trees automatic everytime on the Ground of my TerrainGrid …
So i write my Code
Vector3f treeLoc = new Vector3f(FastMath.nextRandomInt(-200,200),0,FastMath.nextRandomInt(-200,200));
treeLoc.setY(terrain.getHeight(new Vector2f(treeLoc.x,treeLoc.z)));
This is ofc only a piece of the Code but will explain all what is to need.
But treeLoc.y is NaN (Infinite?).
So i tried a few things like get the High of the generated quad and and more but everything is giving only NaN …

Now my Question … How ! i Can get this working ? … Or what is the right way to get the Y of a endless Terrain that using Quads so i can place my Trees everytime on the ground and not flying in the Air ? .… Please maybe with a Code example ?
Cause iam frustrated about to try out much much things… Hopefully someone can help me here :slight_smile:
I searched a little Time here but when i missed a Post please let me know.

Lovely Sy