For this sort of misshap I use Chuck's fix, gap filling CA. If you hold the 2 parts together you will more than likely find that they fit back together easily, so don't try to trim them.
Mal
EDIT: Kevin's fix will work, but, especially if there are thin slivers of plastic, the mating surfaces will be altered (by the melting action of the cement) and you will have a simple but joint, rather than a mechanical interlock.....lockey......type......thing. Not a major deal with this item but can be with say an undercarriage leg.