Merge pull request #1947 from matrix-org/t3chguy/invite_checkIfAlone

re-run checkIfAlone if a member change occurred in the active room

src/components/structures/RoomView.js

@@ -675,6 +675,7 @@ module.exports = React.createClass({
         }
 
         this._updateRoomMembers();
+        this._checkIfAlone(this.state.room);
     },
 
     onRoomMemberMembership: function(ev, member, oldMembership) {