single info window fails if popup:true on marker
when adding a stack of markers to the map,
and in my case setting the first marker to popup:true
the feature to show only 1 info window at a time fails.
clicking a second marker opens a second window
but, after closing that first window, the single info window works as expected.
it is as if the manually popped window, is not taken into account when handling
single info window functionality.
