js报错uncaught typeerror: cannot read property ‘length’ of null

先上问题代码：

fmt_customerLaber : function (column,row){
                    var cuslaber ="";
                    if( row.cusLabelList  ！= null && row.cusLabelList.length > 1){
                        var len = row.cusLabelList.length -1;
                        for (var i=len;i>=0;i--){
                            cuslaber += row.cusLabelList[i].labelName+",";
                        }
                        console.log(cuslaber);
                        return cuslaber.substring(0, cuslaber.lastIndexOf(','));;
                    } else{
                        return '无';
                    }
                }