Close language selector if group selector is opened

e.stopPropagation is harmful and causes problems like this.
It was used to prevent the dialog being closed immediately.
Instead, use a check in hide to ignore clicks on the trigger.
Clicks inside the dialog still use e.stopPropagation.

Small optimization with firstShow to not re-rerender the list
each time it is opened.

Bug: T47699
Change-Id: Idbbecb9c6c97cd301e4b53948098e5e27816cb95