error - TypeError: this is undefined 'r'

[arjmandian]

Dear,
I'm using nuxt.js and I got this error I think there is a conflict.

error:
TypeError: this is undefined
r metisMenu.min.js:8
code:
v = function () {
function r(e, n) {
this.element = e, this.config = a({}, f, {}, n), this.transitioning = null, this.init()
}

        var e = r.prototype;

Please, how can I solve this issue

Thank you