odrefresh: minor diagnostic improvements

Fix potentially unchecked access to the value of a std::optional
field.

Log the ART APEX version when checking artifacts. Useful for issues
without a bugreport.

Bug: 197489543
Test: boot & check logcat, manually test with broken xml derived C++
Change-Id: I7691d9eaa52206b125760e414f065be9d0358009
1 file changed