Errors when integrating fieldgroup rows on "Manage fields" screen

I have an issue on fieldgroup that occurs on the fields-overview screen. When dragging the fields there, onDrop gives an js-error on the rowHandler.
rowHandlers.field is not a constructor
[Break on this error] var rowHandler = eval('new rowHa... + data.rowHandler + '(row, data);');

Now there are a couple of ways to look at this.
1/ A very easy fix:

Drupal.fieldUIOverview = {
     // ... So here check if the function exists. 
      if (typeof(eval('rowHandlers.' + data.rowHandler)) == 'function') {
        // Create the row handler, make it accessible from the DOM row element.
        var rowHandler = eval('new rowHandlers.' + data.rowHandler + '(row, data);');
        $(row).data('fieldUIRowHandler', rowHandler);       
      }   

Eval will not give the actual error that occured, so by checking the type of the var will tell us if it is a function. That's the only way i know in js to really have the expected result.

2/ Field_group's extra attach goes like this on the fields overview:

Drupal.behaviors.fieldUIFieldsOverview = {
  attach: function (context, settings) {
    $('table#field-overview', context).once('field-field-overview', function() {
      Drupal.fieldUIOverview.attach(this, settings.fieldUIRowsData, Drupal.fieldUIFieldOverview);
    });
  }
};

So you could say, ok to alter the onChange or onDrop, or maybe not even hooking the format trigger for fields in that form, i could create my own object as well.
Drupal.fieldUIOverview.attach would be Drupal.fieldGroupUIOverview.attach or something.

What do you think? (i provided a patch for the js check if you find option 1 the best for all other contribs that want to do exotic stuff.)