fixed #74 and a problem with lost rooms

sails/src/api/hooks/rooms.js

@@ -168,7 +168,8 @@ module.exports = function roomsHook (sails) {
     * Call from config/sockets.js after a socket disconnects
     */
     disconnect: function(socket) {
-      var rooms = socketRooms[sails.sockets.getId(socket)];
+	var rooms = socketRooms[sails.sockets.getId(socket)];
+	if (!rooms) return;
       for (var i = 0; i < rooms.length; i++)
          sails.hooks.rooms.unsubscribeFromRoom(rooms[i].room, socket);
     }

sails/src/assets/scripts/modules/student/controllers/collections.js

@@ -322,7 +322,10 @@ dashboardControllers.controller('StudentCollectionsCtrl', function StudentCollec
     // Returned data from the modal window
     modalInstance.result.then(function (pictoId) {
 
-      // Send the picto to the server
+	if (!pictoId)
+	    return;
+
+	// Send the picto to the server
       $http.put(config.backend + '/stu/' + $scope.studentData.id + '/cat', {
         prev_id_stu_pic: picto_cat.id,
         new_id_pic: pictoId