Fix references to 'this' in Avatar and Unread

src/Avatar.js

@@ -32,7 +32,7 @@ export function avatarUrlForMember(member, width, height, resizeMethod) {
         // member can be null here currently since on invites, the JS SDK
         // does not have enough info to build a RoomMember object for
         // the inviter.
-        url = this.defaultAvatarUrlForString(member ? member.userId : '');
+        url = defaultAvatarUrlForString(member ? member.userId : '');
     }
     return url;
 }

src/Unread.js

@@ -77,7 +77,7 @@ export function doesRoomHaveUnreadMessages(room) {
             // that counts and we can stop looking because the user's read
             // this and everything before.
             return false;
-        } else if (!shouldHideEvent(ev) && this.eventTriggersUnreadCount(ev)) {
+        } else if (!shouldHideEvent(ev) && eventTriggersUnreadCount(ev)) {
             // We've found a message that counts before we hit
             // the user's read receipt, so this room is definitely unread.
             return true;