"This matrix cannot be inverted"

I want to display a particle emitter on the GUI node, which sort of works.

But when I make collision tests on the particle-emitting quad I get this and have no idea of what it means or how to solve it:

java.lang.ArithmeticException: This matrix cannot be inverted
    at com.jme3.math.Matrix4f.invert(Matrix4f.java:1455)
    at com.jme3.math.Matrix4f.invert(Matrix4f.java:1427)
    at com.jme3.collision.bih.BIHTree.collideWithBoundingVolume(BIHTree.java:460)
    at com.jme3.collision.bih.BIHTree.collideWith(BIHTree.java:474)
    at com.jme3.scene.Mesh.collideWith(Mesh.java:959)
    at com.jme3.scene.Geometry.collideWith(Geometry.java:448)

Well, it’s trying to invert the world matrix which should be invertible … Unless you have like a scale of zero or something.