I am trying to use this menu for mobile on a site.
http://tympanus.net/codrops/2013/08/13/multi-level-push-menu/comment-page-8/#comment-466199

I have it working but one ie11 user is reporting an error and i am seeing the following error in console
Uncaught TypeError: Cannot read property 'querySelectorAll' of nullmlPushMenu._init @ mlpushmenu.js:89mlPushMenu @ mlpushmenu.js:67(anonymous function) @ (index):1062

Here is a snippet of the js file in question

function mlPushMenu( el, trigger, options ) {   

    this.el = el;

    this.trigger = trigger;

    this.options = extend( this.defaults, options );

    // support 3d transforms

    this.support = Modernizr.csstransforms3d;

    if( this.support ) {

        this._init();

    }

}



mlPushMenu.prototype = {

    defaults : {

        // overlap: there will be a gap between open levels

        // cover: the open levels will be on top of any previous open level

        type : 'overlap', // overlap || cover

        // space between each overlaped level

        levelSpacing : 40,

        // classname for the element (if any) that when clicked closes the current level

        backClass : 'mp-back'

    },

    _init : function() {

        // if menu is open or not

        this.open = false;

        // level depth

        this.level = 0;

        // the moving wrapper

        this.wrapper = document.getElementById( 'mp-pusher' );

        // the mp-level elements

        this.levels = Array.prototype.slice.call( this.el.querySelectorAll( 'div.mp-level' ) );

        // save the depth of each of these mp-level elements

        var self = this;

        this.levels.forEach( function( el, i ) { el.setAttribute( 'data-level', getLevelDepth( el, self.el.id, 'mp-level' ) ); } );

        // the menu items

        this.menuItems = Array.prototype.slice.call( this.el.querySelectorAll( 'li' ) );

        // if type == cover these will serve as hooks to move back to the previous level

        this.levelBack = Array.prototype.slice.call( this.el.querySelectorAll( '.' + this.options.backClass ) );

        // event type (if mobile use touch events)

        this.eventtype = mobilecheck() ? 'touchstart' : 'click';

        // add the class mp-overlap or mp-cover to the main element depending on options.type

        classie.add( this.el, 'mp-' + this.options.type );

        // initialize / bind the necessary events

        this._initEvents();

    },

the specific line 89 is in the middle of that so here it is pulled out for your orientation

this.levels = Array.prototype.slice.call( this.el.querySelectorAll( 'div.mp-level' ) );

I have then called the instance of the plugin in my footer (thats the index line 1082

that call looks like this

<script>

    new mlPushMenu(

        document.getElementById( 'mp-menu' ),

        document.getElementById( 'trigger' ),

        { type : 'cover' }

    );

</script>