Handle cleared preresolved strings

The profile saver can theoretically result in the preresolved strings
being cleared before they are updated. Since the clearing process
nulls the array, it was causing a null pointer dereference in some
cases.

(cherry-picked from commit 77f84fcc257bba0b40cb123a748ecbd0a96726b2)

Bug: 134698657
Test: test-art-host
Merged-In: I9c260bbfded26e9481381e9978596907e48c3307
Change-Id: I9c260bbfded26e9481381e9978596907e48c3307