bug: Unguarded optional-field access can white-screen the mentors and landing pages

[yingliu-data]

Bug Report

Unguarded property access can white-screen the whole mentors page and the landing page when a record omits optional fields (the backend serializes with JsonInclude.NON_NULL, so absent fields arrive as missing keys).

• src/components/MentorProfileCard.tsx — line 98 mentor.images[0]?.path (throws if images itself is absent), line 187 mentor.country.countryName, line 190 mentor.network.map(...), line 226 mentor.skills.yearsExperience (line 114 defensively uses skills?. but 226 doesn't), line 230 mentor.spokenLanguages.length, line 271 mentor.menteeSection.additional.
• src/components/EventContainer.tsx:65 event.endDate.split(', '), line 71 event.speakerProfile.label; src/components/EventCard.tsx:67,77 images[0].path. Backend Event.speakerProfile is nullable.

Reproduction

• A mentor record with a null network/images/country → one bad mentor throws during render → the entire /mentorship/mentors list white-screens.
• A CMS event with no speaker/images/endDate → the home page throws during render (SSR 500 / client crash).

Severity

Medium

Potential Risk

• A single sparse record takes down an entire public page.

Suggested Fix

• Guard all optional-field access with optional chaining / defaults, consistently (e.g. mentor.images?.[0]?.path, mentor.network?.map, event.speakerProfile?.label).
• Consider normalizing API responses (default missing arrays to []) at the fetch boundary.
• Add tests rendering mentor/event cards from minimal payloads.

Registration-side complement to #271 (rendering existing images); this covers crashes on sparse data across cards.