Fix CTS crash from DexFile refactoring

Avoid path to nullptr access introduced by the previous refactoring.

Bug: 22322814
Change-Id: Id8874b26c072a11b0494e8126f8b0602a7c5b9e8
Test: m test-art-host, cts-tradefed run cts --skip-preconditions --skip-device-info --module vm-tests-tf
3 files changed