Fixed the previous fix of the anti-nag hook

[imcrazytwkr]

✍️ Description

Yesterday's fix of the anti-nag apt hook had some unintended side effects as reported today by @memesalot and @vsc55 in #6078. This PR fixes this. What is being done in particular:

• && chaining is replaced back with an if-condition because otherwise the hook returns with a non-0 exit code when JS patching is not needed and apt scares users with an error message
• dpkg -V check has been replaced with a grep -F check to avoid stdout leaking ??5?????? /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js (I couldn't reproduce that on my installs, glad others helped with testing)

Draft until this concern by @vsc55 is resolved:

I mean that the new sed syntax is not compatible with older versions of the pve js file.

🔗 Related PR / Issue

Link: #6078
Link: #6084

✅ Prerequisites (X in brackets)

• Self-review completed – Code follows project standards.
• Tested thoroughly – Changes work as expected. This time also tested by @vsc55: message link
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.

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🛠️ Type of Change (X in brackets)

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing functionality in a way that may require updates.
• 🆕 New script – A fully functional and tested script or script set.
• 🌍 Website update – Changes to website-related JSON files or metadata.
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, AppName.md, CONTRIBUTING.md, or other docs.

[memesalot]

Fixes the ??5?????? issue for me! Thanks!

[vsc55]

Hi @imcrazytwkr,
I have tried it with the oldest version of proxmox 8.0.3 and it breaks when applying.

Change const subscription = ! ( to const subscription = = ( generating an error in the browser.