fix: set a default for the current menu in Drilldown before it is used
fix: set a default for the current menu in Drilldown before it is used

`$currentMenu` is used by `_getMaxDims`.

Changes: move `$currentMenu` initialization to `_init()`

denisahac/foundation-sites,denisahac/foundation-sites,colin-marshall/foundation-sites,colin-marshall/foundation-sites,DaSchTour/foundation-sites,colin-marshall/foundation-sites,zurb/foundation,denisahac/foundation-sites,zurb/foundation,zurb/foundation-sites,abdullahsalem/foundation-sites,zurb/foundation-sites,abdullahsalem/foundation-sites,zurb/foundation-sites,DaSchTour/foundation-sites,zurb/foundation,abdullahsalem/foundation-sites