Fixed at https://github.com/cocos2d/cocos2d-x/pull/3442.

It’s because when extending cc.ScrollView in JS, cc.ScrollView.extend will create an object as prototype.

cc.Class.extend = function (prop) {
    var _super = this.prototype;

    // Instantiate a base class (but only create the instance,
    // don't run the init constructor)
    initializing = true;
    var prototype = new this(); // XXX, ScrollView in native will be just allocated, but without initialization. So the _touches is NULL.

We need to check whether the _touches is NULL in the destructor of ScrollView.