Since the dive-site-filter is active either on the dive-site-edit page or the dive-site-list page, use that as the flag for dive-site-edit mode. Moreover, when the filter is reset, the MapWidgetHelper::reloadMapLocations() function is called, so we can use that place to enter/exit edit mode. This makes it easier to keep everything consistent. Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>