particleEmitter().onCollision() { } appears to have no effect upon object within closure

Actual behavior:

Running the following code with 2.0.7 runJvm, circle color change does not take place when circle object collides with any part of particleEmitter object.

```
val circle = circle(radius= 20.0, Colors.RED)

val emitter = resourcesVfs["./particle/particle.pex"].readParticleEmitter()

particleEmitter(emitter).position(views.virtualWidth * 0.5, views.virtualHeight * 0.75).onCollision( {it == circle}) {
circle.color = Colors.BLUE
}

circle.addUpdater {
circle.color = Colors.RED
x = mouseX - circle.radius
y = mouseY - circle.radius
}
```
code adapted from [KorGE Tutorial #5 Simple collision detection](https://www.youtube.com/watch?v=F1AXdD5bLjA) video and [korge-samples particle emitter](https://github.com/korlibs/korge-samples) code.

Expected behavior: Best case would be circle shape changes color when collision detected with base shape and particle flow. Next best case would be circle shape changes color when collision detected with base shape.

Start by running the supplied runJvm reproduction with particle/particle.pex, then compare it with the linked KorGE collision tutorial and particle-emitter sample. Trace particleEmitter(...).onCollision to determine which collision cases it handles; done means the callback changes the circle color for the documented base-shape or particle collision.

Written by the indexing model from the issue text.