Remove <a> when contact_web is equal to '-'

Fix https://github.com/geoadmin/mf-geoadmin3/issues/1235

https://mf-chsdi3.dev.bgdi.ch/ltteo/rest/services/lubis/MapServer/ch.swisstopo.lubis-luftbilder-dritte-kantone/20128810167423/htmlPopup?imageDisplay=1920,636,96&lang=de&mapExtent=663253.81,191397.5,672853.81,194577.5