Fix TypeScript errors from no-non-null-assertion fixes

Two fixes introduced by the non-null assertion cleanup produced type
errors:

- scoring-event.ts: `?? ""` was wrong type for a participant object map;
  restructured to explicit null guards so TypeScript can narrow correctly
- standings-sync/index.ts: `?? null` after name-match lookup lost the
  truthy guarantee, causing TS18047 on the write-back block; added
  `participant &&` guard before accessing its properties

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/models/scoring-event.ts

@@ -498,11 +498,13 @@ export async function getUpcomingEventsForDraftedParticipants(
 
     const pMap = participantsByEvent.get(row.id);
     if (pMap) {
-      if (row.participant1Id && draftedMap.has(row.participant1Id)) {
-        pMap.set(row.participant1Id, draftedMap.get(row.participant1Id) ?? "");
+      if (row.participant1Id) {
+        const p1 = draftedMap.get(row.participant1Id);
+        if (p1) pMap.set(row.participant1Id, p1);
       }
-      if (row.participant2Id && draftedMap.has(row.participant2Id)) {
-        pMap.set(row.participant2Id, draftedMap.get(row.participant2Id) ?? "");
+      if (row.participant2Id) {
+        const p2 = draftedMap.get(row.participant2Id);
+        if (p2) pMap.set(row.participant2Id, p2);
       }
     }
 

app/services/standings-sync/index.ts

@@ -86,7 +86,7 @@ export async function syncStandings(sportsSeasonId: string): Promise<SyncResult>
       if (matchedName) {
         participant = participantByName.get(matchedName) ?? null;
         // Write-back: persist externalId so future syncs skip name matching for this team
-        if (!participant.externalId) {
+        if (participant && !participant.externalId) {
           await updateParticipant(participant.id, { externalId: record.externalTeamId });
         }
       }