Stencyl v03 Collision

Anyone had any problems with collision in v3.0?  when the missiles hits an object it is meant to kill the missile and create and explosion actor, at the moment the missile is killed but the explosion actor is not created, however when I take out the Kill block, it will create the explosion but repeatedly because the missile isn't killed and is constantly colliding. Any ideas how to kill and actor and switch to another actor in V3.0, because it worked in 2.3.  many thanks.

You should be able to do (in the actor):

when self collides with actor of type missile
   create explosion actor at x of self, y of self
   kill [actor of type]
   kill self

Hi,   when I kill the actor it comes up with the error message Critical Error: Null Object Reference, makes no sense.  only started doing this in v3.0, gonna have to go back to a much earlier version and rebuild the game i think 

Screenshot of the code?