Merge "Revert "When deregister bta_sys_deregister set nullptr"" am: 89caf445 am: 73bf4252

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/2479098



Change-Id: I9065c1089b1d005aa8f66d6aaebe2e921cb4d292
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>