Conform more code to strict null checking (#10169)

* Conform more code to strict null checking

* delint

* Iterate

* delint

* Fix bad test

test/components/views/rooms/MemberList-test.tsx

@@ -37,7 +37,7 @@ function generateRoomId() {
 
 describe("MemberList", () => {
     function createRoom(opts = {}) {
-        const room = new Room(generateRoomId(), null, client.getUserId());
+        const room = new Room(generateRoomId(), client, client.getUserId()!);
         if (opts) {
             Object.assign(room, opts);
         }

test/components/views/rooms/MessageComposer-test.tsx

@@ -370,7 +370,7 @@ describe("MessageComposer", () => {
                 replyToEvent = mkEvent({
                     event: true,
                     type: EventType.RoomMessage,
-                    user: cli.getUserId(),
+                    user: cli.getUserId()!,
                     content: {},
                 });
 

test/components/views/rooms/RoomHeader-test.tsx

@@ -377,7 +377,7 @@ describe("RoomHeader (React Testing Library)", () => {
                 content,
             });
             room.addLiveEvents([event]);
-            return { event_id: event.getId() };
+            return { event_id: event.getId()! };
         });
 
         alice = mkRoomMember(room.roomId, "@alice:example.org");