Fixed mentor and member names sometimes showing as "undefined undefined"

If a mentor or member profile was ever missing a first or last name -- an incomplete profile that skipped past that step -- several places across the site (page titles, search-result descriptions, structured data used by search engines, and image alt text) could literally show the text "undefined undefined" instead of nothing. We found and fixed every place this could happen with one shared, consistent fallback, rather than patching each spot differently. A profile missing both names now falls back to a plain default instead of ever showing broken-looking text.