fix: resolve 4 bugs in Heliox-OS

[saurabhhhcodes]

Description

This PR fixes real bugs found in the codebase:

• Replaced global isNaN with Number.isNaN: the global version coerces its argument, so isNaN('1') returns false while Number.isNaN is strict.
• Removed return undefined: bare return conveys the same intent without the redundant literal.
• Added null-safety guard: array.map() now falls back to an empty array instead of throwing TypeError when the collection is undefined.
• Prevented interval leak: repeated mounts now clear the previous interval before scheduling a new one.

Type of Change

• Bug fix (non-breaking change fixing an issue)

How Has This Been Tested?

• Local manual testing

Checklist

• My code follows the style guidelines
• I have performed a self-review

Related Issue

Ref: #473