Undefined index type error in media_form_field_ui_field_edit_form_alter()

An error is displayed when editing an entity reference field for the Commerce Coupon module:

Notice: Undefined index: type in media_form_field_ui_field_edit_form_alter() (line 375 of /sites/all/modules/media/media.module).

This is due to $form['instance']['widget']['type'] not being defined for the default coupon field.

I've included a patch for fixing this in the Media module, but can also understand if the position is this really should be defined in Commerce Coupon. I'm not really sure why they chose to create the entity field without defining a type, other than it wasn't really needed.

See attached, thanks.