Steps to reproduce the issue

I tried to include Module Position field inside a Repeatable field.

Expected result

The repeatable module is show up and then when module position button is clicked the modal is show up and I'm able to add a module position

Actual result

The module position modal is showed up but the available module options are not clickable.

When I looked at the browser console I found this error message :
Uncaught TypeError: Cannot set property 'value' of nulljSelectPosition_jform_params_position @ index.php?option=com_templates&view=style&layout=edit&id=9:93onclick @ index.php?option=com_modules&view=positions&layout=modal&tmpl=component&function=jSelectPosition_jf…:108

System information (as much as possible)

Chrome 43
Mac OSX Yosemite

Additional comments

I have recorded a screencast please have a look here https://www.dropbox.com/s/cuhftczjjemtmu0/jbug.mp4?dl=0