fix: default avatar relative url

react/features/base/avatar/components/web/Avatar.js

             <img
                 className = { this._getAvatarClassName('defaultAvatar') }
                 id = { this.props.id }
-                src = '/images/avatar.png'
+                src = 'images/avatar.png'
                 style = { this._getAvatarStyle() } />
         );
     }