prometheus-node-exporter-lua: check if status is nil before processing wifi device metrics interfaces

[oowl]

Add a check for status existence before processing.

In my OpenWRT device, it did not have a Wi-Fi device, so if I use prometheus-node-exporter-lua, I found below error in my syslog.

📦 Package Details

Maintainer: @
_{(You can find this by checking the history of the package Makefile.)}

Description:

---

🧪 Run Testing Details

• OpenWrt Version:
• OpenWrt Target/Subtarget:
• OpenWrt Device:

---

✅ Formalities

• I have reviewed the CONTRIBUTING.md file for detailed contributing guidelines.

If your PR contains a patch:

• It can be applied using git am
• It has been refreshed to avoid offsets, fuzzes, etc., using

  make package/<your-package>/refresh V=s

• It is structured in a way that it is potentially upstreamable
  _{(e.g., subject line, commit description, etc.)
  We must try to upstream patches to reduce maintenance burden.}

[systemcrash]

@oowl properly name your commit subject after squashing the two commits.

[oowl]

@systemcrash Done, Sir. PTAL

[champtar]

@oowl I've edited the PR title, please edit your commit title to start with prometheus-node-exporter-lua

[oowl]

@champtar done

[systemcrash]

I thought you already did it but please fix your commit SOB.

[oowl]

@systemcrash Sorry, I did not understand your requirement. I have been squashing my commits into one commit and also changed my PR title with proper words.

I thought you already did it but please fix your commit SOB.

SOB seems offensive words? mean Son of Bitch?

[systemcrash]

https://openwrt.org/docs/guide-developer/working-with-github-pr