There's a couple of things you wanna make sure is correct with your height map before putting it in the game, otherwise it will crash.
- Make sure your image is the correct size. I believe the image should be 513x513 pixels
- Flatten your image/merge all layers. If the image is not flattened, FH will crash
- Make sure the name of your heightmap contains "Terrain" in it. So for an example, your image should be called "namehereTerrain.PNG"
- Make sure the image is saved as a .PNG, and saved in FeralHeart>Media>Terrains
I hope this helps to sort out the problem. If it doesn't work still, please let me know and I'll be happy to help your further ^u^