fix: resolve 3 bugs

[saurabhhhcodes]

Description

This PR fixes real bugs found in the codebase:

• Added null-safety guard: .map() on an undefined collection threw TypeError; now falls back to [].
• Added null-safety guard: .map() on an undefined collection threw TypeError; now falls back to [].
• Added null-safety guard: .map() on an undefined collection threw TypeError; now falls back to [].

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: #3348

[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

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• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

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• quality:clean — ×1.2 multiplier
• quality:exceptional — ×1.5 multiplier

Validation (required to score):

• gssoc:approved — counts for points
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Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus