R1:02315c4c48b9

Fix double-close on dialogs leading to Javascript console error

Summary:
Ref T13302. The "Close/Cancel" button is currently running two copies of the "dismiss dialog" code, since it's techncally a link with a valid HREF attribute.

An alternate formulation of this is perhaps `if (JX.Stratcom.pass()) { return; }` ("let other handlers react to this event; if something kills it, stop processing"), but `pass()` is inherently someone spooky/fragile so try to get away without it.

Test Plan: Opened the…