Using center throws an error

[brentmiller1973]

When you set the center attribute to true, code is throwing an error at this line on completion of a polyline:
var pathWidth = this._path.getBBox().width;
I guess you can't get the width of a path element (it only has coordinates)....so I changed the above line to this and it works now:

//Fix:
var pathWidth = this._path.getBoundingClientRect().width;

[leplatrem]

Thanks for reporting and providing a fix !