Fix issue with repeated closing of modal window [MJ-198]

The event for closing the modal window was getting fired twice, once for clicking the close button and once for the window hiding itself.

Handling the modal hide event is necessary to cover the many methods that the user could close the window (pressing `Esc', clicking on the darkened modal background, clicking 'x' in the top right, etc). Since clicking on the close button results in the modal getting hidden anyway, the click event can be removed with no issue.