matching: don't throw but return as unmatched if picking StopTimeUpdates failed 🐛

Often `matchingSTUN` is missing because `tripUpdate.stop_time_update[]` is too small. This is perfectly valid (albeit unusable) input for gtfs-rt-feed, so we merely log this as a failed matching instead of an erroneous matching.

follow-up of f1d76b3

Author: derhuerst

lib/match-with-schedule-trip.js

@@ -1,5 +1,5 @@
 import {createHash} from 'node:crypto'
-import {deepStrictEqual, ok} from 'node:assert/strict'
+import {deepStrictEqual} from 'node:assert/strict'
 import {DateTime} from 'luxon'
 import maxBy from 'lodash/maxBy.js'
 import {
@@ -583,9 +583,31 @@ const createMatchGtfsRtTripUpdateWithScheduleStopTimes = async (cfg, opt = {}) =
 			snapRange: 5, // todo: make customisable
 		}, tripUpdate)
 		const matchingSTU0 = tripUpdate.stop_time_update[iMatchingSTU0]
-		ok(matchingSTU0, `StopTimeUpdate matchingSTU0 (${iMatchingSTU0}) should exist`)
+		if(!matchingSTU0) {
+			logger.warn({
+				...logCtx,
+				iMatchingSTU0,
+				matchingSTU0,
+			}, `not trying to match because StopTimeUpdate matchingSTU0 (${iMatchingSTU0}) is missing`)
+			return {
+				tripUpdate,
+				isMatched: false,
+				isCached: false,
+			}
+		}
 		const matchingSTUN = tripUpdate.stop_time_update[iMatchingSTUN]
-		ok(matchingSTUN, `StopTimeUpdate matchingSTUN (${iMatchingSTUN}) should exist`)
+		if(!matchingSTUN) {
+			logger.warn({
+				...logCtx,
+				iMatchingSTUN,
+				matchingSTUN,
+			}, `not trying to match because StopTimeUpdate matchingSTUN (${iMatchingSTUN}) is missing`)
+			return {
+				tripUpdate,
+				isMatched: false,
+				isCached: false,
+			}
+		}
 		const stopTimes = [
 			[
 				'st' + iMatchingSTU0, // alias