Don't close the compose box on right click in Firefox.

Trac #1737

Firefox has the slightly broken behavior that it emits a click event on
the document when you right click, but not on any of the child nodes, so
our #compose stopPropagation doesn't stop right-click events from closing
compose. Chrome never emits click events on right click.

(imported from commit 2519c542715c93877b6d38e5dcff1f3e011688e4)

static/js/ui.js

@@ -1522,6 +1522,13 @@ $(function () {
     // End Webathena code
 
     $(document).on('click', function (e) {
+        if (e.button !== 0) {
+            // Firefox emits right click events on the document, but not on
+            // the child nodes, so the #compose stopPropagation doesn't get a
+            // chance to capture right clicks.
+            return;
+        }
+
         // Dismiss popovers if the user has clicked outside them
         if ($('.popover-inner').has(e.target).length === 0) {
             popovers.hide_all();