mwan3: prevent NaN in rpcd status for empty state files - #30800

Checking PR #30800: mwan3: prevent NaN in rpcd status for empty state files (Makefile Audit)

Commit e68a724 - mwan3: return zero for empty integer state:

✅ Makefile does not assign per-package variables at the top level
✅ Makefile contains valid assignment operators and no spaces after ':='
✅ No feed package forces its own inclusion into buildbot default images via DEFAULT+BUILDBOT
✅ Makefile does not reuse PKG_NAME in call, define, or eval lines
✅ File additions are text
✅ File additions contain clean UNIX (LF) line termination
✅ All modified files contain a trailing newline

Package Release Audit:

✅ Package net/mwan3 version unchanged, but PKG_RELEASE bumped from '2' to '3'