Remove the export kml button in IE9

Fix for https://github.com/geoadmin/mf-geoadmin3/issues/1866

(IE9 does not support file save functionality and thus can't export kml. Note however, that a drawing can be send by email in the feedback tool)
It could be truthy but not a number so the !gaBrowserSniffer.msie would not work. I use isNaN because it's also used in the browserSniffer (and probably elsewhere as well).