ui.js: fix duplicate event on mouse click

On clicks, the YouTube app generates key events with keyCode 13 ("OK"
button). We should not be sending our own click events for these, as
they already exist.

src/ui.js

@@ -83,8 +83,13 @@ function createOptionsPanel() {
       if (evt.keyCode in ARROW_KEY_CODE) {
         navigate(ARROW_KEY_CODE[evt.keyCode]);
       } else if (evt.keyCode === 13) {
-        // "OK" button
-        document.querySelector(':focus').click();
+        // The YouTube app generates these "OK" events from clicks (including
+        // with the Magic Remote), and we don't want to send a duplicate click
+        // event for those. It seems isTrusted is only true for "real" events.
+        if (evt.isTrusted === true) {
+          // "OK" button
+          document.querySelector(':focus').click();
+        }
       } else if (evt.keyCode === 27) {
         // Back button
         showOptionsPanel(false);