Do not propagate click events that close a modal

When a modal dialogue is open (e.g. after selecting "Reply by email" from Issue action menu), clicking outside the modal will close it. However, in addition to closing the modal, Kunagi executes the click as a normal event (e.g. the area outside the modal is occupied by a collapsed block, the block is expanded).

Closing the modal is intended behaviour, but the click should not be propagated further.