Merge "Fix nullptr access when cow reader open fails" am: 9e6005ad am: 9d1460be am: cadcf82f

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2325397



Change-Id: Ie300c9cbd6d5b43c6cb458f325d6b0160e61fcf3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>