1018: Avoid assertion failure in SELECT pop-up for non-current tab

1018: Avoid assertion failure in SELECT pop-up for non-current tab

Check in refresh_view() whether the tab is still current; if not, skip
the draw_doc() and draw_frames() calls because draw_current_link()
called within them asserts that the tab is current.  However, do
always call print_screen_status(), because that handles non-current
tabs correctly too.

I think it was not yet possible to trigger the assertion failure with
setTimeout, because input.value modifications by ECMAScript do not
trigger a redraw (bug 1035).