Prevented null error thingy.

Used info from
http://answers.unity3d.com/questions/410711/trigger-in-child-object-calls-ontriggerenter-in-pa.html
and
http://docs.unity3d.com/Documentation/Components/class-Rigidbody.html .
Gave the child collider its own kinematic rigidbody so that it would not
cause problems with the parent... But it still doesn't work as intended.