NetBpfLoad: fix empty log_buf detection logic am: ea1d8f6376

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

Change-Id: I1c1f570a2539c01158c1bd3686de3f89aa1becda
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>