[stable30] fix: storage wrapper / files scanner do not array access on null

[susnux]

• Resolves: [Bug]: Trying to access array offset on value of type null #50431

Summary

• Do not try to set a value on null
• harden files scanner by checking values correctly and fixing type issues
  • see fix: Harden files scanner for invalid null access #50436

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[susnux]

/backport to stable29