The web UI crashed on load when VITE_NOTIFIER_RELAY was not set
because normalizeRelayUrl(undefined) calls url.match(...) on the
undefined argument, producing:
TypeError: can't access property 'match', A is undefined
Fix: guard with a truthy check before calling normalizeRelayUrl,
and early-return from loadAlerts when NOTIFIER_RELAY is undefined.
Fixes bead mailship-4ic
