Handle nullptr from mapMemory properly

Test: make cts -j123 && cts-tradefed run cts-dev --module \
CtsMediaTestCases --compatibility:module-arg \
CtsMediaTestCases:include-annotation:\
android.platform.test.annotations.RequiresDevice

Bug: 38385699
Change-Id: Ib42492f9d9d162493e565d6d0071cc2a184fb476
2 files changed