Do not try to destroy NULL crypto

The library doesn't like it

Change-Id: I517314dd633352698edcae0adcd9f65e87e65473
Do not free k0 in ClientAuthRXGK

The current contract donates that memory to the security object.

Change-Id: Ic665b7ece81f3c77b2c08a65ebb0035a5b5cb07d