FIX: Don't dismiss headers on modifier keys.

app/assets/javascripts/discourse/components/menu-panel.js.es6

@@ -155,7 +155,7 @@ export default Ember.Component.extend({
   @on('didInsertElement')
   _bindEvents() {
     this.$().on('click.discourse-menu-panel', 'a', e => {
-      if (e.metaKey) { return; }
+      if (e.metaKey || e.ctrlKey || e.shiftKey) { return; }
       if ($(e.target).data('ember-action')) { return; }
       this.hide();
     });

app/assets/javascripts/discourse/lib/click-event.js.es6

@@ -0,0 +1,3 @@
+export function isModifierOrMetaKey(event) {
+  return e.metaKey || e.ctrlKey || e.shiftKey;
+}