fix automatic DM avatar with functional members

src/models/room.ts

@@ -932,25 +932,15 @@ export class Room extends ReadReceipt<RoomEmittedEvents, RoomEventHandlerMap> {
 
     public getAvatarFallbackMember(): RoomMember | undefined {
         const functionalMembers = this.getFunctionalMembers();
-        // Optimizing for performance, we iterate over all members outermost, as is it the longest of the 3 lists we are comparing.
-        const nonFunctionalMemberCount = this.getMembers()!.reduce((count, m) => {
-            if (
-                m.membership &&
-                // We care most about big rooms where also possibly lots of users may have left,
-                // so we first do the O(2) membership check, as it is definitely cheap and might remove candidates before the next step.
-                ["join", "invite"].includes(m.membership) &&
-                // Then we do the O(functionalMembers.length) functionalMember check, which is probably usually still cheap.
-                !functionalMembers.includes(m.userId)
-            ) {
-                return count + 1;
-            }
-            return count;
-        }, 0);
 
         // Only generate a fallback avatar if the conversation is with a single specific other user (a "DM").
-        if (nonFunctionalMemberCount > 2) {
-            return;
-        }
+        let nonFunctionalMemberCount = 0;
+        this.getMembers()!.forEach((m) => {
+            if (m.membership !== "join" && m.membership !== "invite") return;
+            if (functionalMembers.includes(m.userId)) return;
+            nonFunctionalMemberCount++;
+        });
+        if (nonFunctionalMemberCount > 2) return;
 
         // Prefer the list of heroes, if present. It should only include the single other user in the DM.
         const nonFunctionalHeroes = this.summaryHeroes?.filter((h) => !functionalMembers.includes(h));