NetBpfLoad: fix empty log_buf detection logic am: ea1d8f6376 am: 57f4aac919

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3256443

Change-Id: Ib09663deac64629fd02e3ce6dd3d82198b55b79c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>