Fix errorprone warnings that should be errors am: a8f72f0e21 am: e5a326cd96

Original change: https://android-review.googlesource.com/c/platform/external/nanohttpd/+/2254824

Change-Id: I927b5a72eeff6e9dcc9ae01f8040a1858fdc078d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>