Drop 11 more non-null assertions across 5 files

- ErrorPage.tsx: FALLBACK_CONFIG literal instead of ERROR_CONFIG["500"]!
- ErrorBoundary.tsx: hoist FALLBACK_RU / FALLBACK_EN to consts so
  pickStrings returns them without the bang.
- routesToPolylines.ts: narrow spider-mode block on filterState.departure
  truthy; guard each route-code lookup.
- FlightsMapStartPage.tsx: narrow firstRoute/depCode/arrCode together
  instead of asserting each individually.
- OnlineBoardDetailsPage.tsx: IIFE over legs[i+1] for TransferBar;
  `_canonicalOrigin` prefix for currently-unused prop.

Warning count: 30 → 19.

src/features/flights-map/components/FlightsMapStartPage.tsx

@@ -238,9 +238,10 @@ export const FlightsMapStartPage: FC<FlightsMapStartPageProps> = ({
     if (!filterState.departure || !filterState.arrival) return [];
     if (filteredRoutes.length === 0) return [];
 
-    const first = filteredRoutes[0]!.route;
-    const depCode = first[0]!;
-    const arrCode = first[first.length - 1]!;
+    const firstRoute = filteredRoutes[0]?.route;
+    const depCode = firstRoute?.[0];
+    const arrCode = firstRoute?.[firstRoute.length - 1];
+    if (!firstRoute || !depCode || !arrCode) return [];
 
     const depCityCode = getCityCodeByAirportCode(dictionaries, depCode) ?? depCode;
     const arrCityCode = getCityCodeByAirportCode(dictionaries, arrCode) ?? arrCode;

src/features/flights-map/routesToPolylines.ts

@@ -38,12 +38,13 @@ export function routesToPolylines(
   const hasArrival = Boolean(filterState.arrival);
   const isSpiderMode = hasDeparture && !hasArrival;
 
-  if (isSpiderMode) {
-    const fromCode = toCity(filterState.departure!);
+  if (isSpiderMode && filterState.departure) {
+    const fromCode = toCity(filterState.departure);
     const destCodes = new Set<string>();
     for (const r of routes) {
-      if (r.route.length > 1) {
-        const dest = toCity(r.route[r.route.length - 1]!);
+      const last = r.route[r.route.length - 1];
+      if (r.route.length > 1 && last) {
+        const dest = toCity(last);
         if (dest !== fromCode) destCodes.add(dest);
       }
     }
@@ -74,7 +75,10 @@ export function intermediateCityIds(
   const ids = new Set<string>();
   for (const r of routes) {
     if (r.route.length <= 2) continue;
-    for (let i = 1; i < r.route.length - 1; i++) ids.add(toCity(r.route[i]!));
+    for (let i = 1; i < r.route.length - 1; i++) {
+      const code = r.route[i];
+      if (code) ids.add(toCity(code));
+    }
   }
   return [...ids];
 }

src/features/online-board/components/OnlineBoardDetailsPage.tsx

@@ -339,9 +339,11 @@ function FlightLegs({
 
           <FlightDetailsAccordion leg={leg} viewType="Onlineboard" />
         </div>
-        {i < legs.length - 1 && (
-          <TransferBar leg={leg} nextLeg={legs[i + 1]!} viewType={viewType} />
-        )}
+        {(() => {
+          const next = legs[i + 1];
+          if (!next) return null;
+          return <TransferBar leg={leg} nextLeg={next} viewType={viewType} />;
+        })()}
         </Fragment>
       ))}
     </div>
@@ -368,7 +370,7 @@ function getLegs(flight: { routeType: string; leg?: IFlightLeg; legs?: IFlightLe
 export const OnlineBoardDetailsPage: FC<OnlineBoardDetailsPageProps> = ({
   flightId,
   locale,
-  canonicalOrigin,
+  canonicalOrigin: _canonicalOrigin,
 }) => {
   const { t } = useTranslation();
 

src/ui/errors/ErrorBoundary.tsx

@@ -19,9 +19,12 @@ interface ErrorBoundaryState {
  * and fall back to English for any language we don't have coverage
  * for. Mirrors what Angular's global ErrorHandler renders.
  */
+const FALLBACK_RU = { title: "Что-то пошло не так", retry: "Повторить" } as const;
+const FALLBACK_EN = { title: "Something went wrong", retry: "Retry" } as const;
+
 const FALLBACK_STRINGS: Record<string, { title: string; retry: string }> = {
-  ru: { title: "Что-то пошло не так", retry: "Повторить" },
-  en: { title: "Something went wrong", retry: "Retry" },
+  ru: FALLBACK_RU,
+  en: FALLBACK_EN,
   es: { title: "Algo salió mal", retry: "Reintentar" },
   fr: { title: "Une erreur s'est produite", retry: "Réessayer" },
   it: { title: "Qualcosa è andato storto", retry: "Riprova" },
@@ -32,10 +35,10 @@ const FALLBACK_STRINGS: Record<string, { title: string; retry: string }> = {
 };
 
 function pickStrings(): { title: string; retry: string } {
-  if (typeof window === "undefined") return FALLBACK_STRINGS.ru!;
+  if (typeof window === "undefined") return FALLBACK_RU;
   const locale = resolveLocaleFromPath(window.location.pathname);
   const lang = locale ? localeToLanguage(locale) : "ru";
-  return FALLBACK_STRINGS[lang] ?? FALLBACK_STRINGS.en!;
+  return FALLBACK_STRINGS[lang] ?? FALLBACK_EN;
 }
 
 /**

src/ui/errors/ErrorPage.tsx

@@ -58,7 +58,14 @@ const ERROR_CONFIG: Record<string, ErrorConfig> = {
   },
 };
 
-const FALLBACK_CONFIG: ErrorConfig = ERROR_CONFIG["500"]!;
+const FALLBACK_CONFIG: ErrorConfig = {
+  titleKey: "PAGE500.HEADER",
+  descriptionKey: "PAGE500.DESCRIPTION",
+  image: "/assets/img/lady500.png",
+  buyTicketKey: "PAGE500.BUY-TICKET",
+  homeKey: "PAGE500.TO-HOME",
+  supportKey: "PAGE500.SUPPORT",
+};
 
 export interface ErrorPageProps {
   /** HTTP status code ("404", "500", "503"). Unknown codes fall back to 500. */