Can't export a mesh to .fbx I've built a bird for a game I'm working on, and when I tried to export the beak mesh as a .fbx file it gave me this error. 
I've applied all the modifiers to the mesh already.
Here's the file https://drive.google.com/file/d/1Ah650tjjbcC3zb4Rw8fqIuto7U9OsTLZ/view?usp=sharing
I've solved the problem, you have to smart uv project the mesh before exporting.