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

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

✅ Pull request originates from a dedicated feature branch (fix/mwan3-finite-status)

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

✅ Author and committer identities are valid
✅ Commit is not a merge commit
✅ Commit subject layout and length are valid: "mwan3: return zero for empty integer state"
✅ Commit description lines adhere to width formatting rules
✅ Commit contains a valid 'Signed-off-by:' line matching author or committer
⚠️ Warning: No reference link (e.g., upstream release notes, changelog, or history URL) detected in description.
⚠️ Warning: Commit is unsigned or cryptographic signature verification failed (Reason: unsigned). Signing commits is a recommended best practice for verifying identity, but is not mandatory.