@ -579,7 +579,7 @@ function _classCallCheck(instance, Constructor) { if (!(instance instanceof Cons
// remove self from vm's watcher list
// this is a somewhat expensive operation so we skip it
// if the vm is being destroyed.
remove(this.vm._watchers, this);
remove(this.vm && this.vm._watchers, this);
var i = this.deps.length;
while (i--) {
this.deps[i].removeSub(this);