dexoptanalyzer: fix a potential use of nullptr

If oat_file is nullptr here, we can't `GetLocation()` on it. unsure if
there's more descriptive context to add here.

Caught by the static analyzer:
> art/dexoptanalyzer/dexoptanalyzer.cc:375:47: warning: Called C++
object pointer is null [clang-analyzer-core.CallAndMessage]

Bug: None
Test: TreeHugger
Change-Id: Icdae5de4a4e4ff82ad03a247c53fc9583afdfa5d
1 file changed