[automerge] libstagefright: fix heap use after free issue 2p: 2bddcbdd0c 2p: a648552ff0 am: d56cb24c5c

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/20068332

Change-Id: Icf0a9b4d841737adec6c2426794cc02402e0e43b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>