In a particle object's properties you can now set it to spawn an object instead of using its default particle image (very cool!). However, once you've set it to an object in the editor there isn't an explicit way to clear the field and reset to the particle image.
A particle action exists to unset the object back to the particle object so you can ensure it is reset at runtime, but ideally you would be able to clear the property field in the editor.
You can set the object to the same particle object, but it is not obvious if this means you are then spawning child particle objects or reverting to using the particle image, the former having processing overheads. Does anyone know which case is correct? If the former, is there a way to reset the field that I'm missing?