More native stack dump hardening.

Threads just starting up or shutting down might not have any managed
stack frames, leading to a NULL "currFrame" frame pointer in the
interpreter stack.

Bug: 8596028

(cherry picked from commit 46371593812d966c40e1ec4019e3c7c6613046a6)

Change-Id: I0fbc6d422bcae0fd080f7c1a63198755235e9e00
1 file changed