ART: Fix 466-get-live-vreg for read barrier.

With the read barrier, the test is actually compiled but it
runs interpreted, so the vreg is successfully retrieved.
Fix the stack visitor to check if we have a compiled frame
before checking if the method is "Optimized".

Change-Id: I600eb7b5c0c2be1b9617e4d05401a711dac01738
1 file changed