title: Add empty overlay to leaflet map?
body: <p>Looking for a way to add an empty overlay to a <code>Leaflet</code> map. I have multiple <code>Leaflet</code> overlays that load in their data from a realtime server. Because I am using a custom UI control and not the default <code>Leaflet</code> one, I have a listener that every time new markers are created, checks to see whether their associated layer is <code>active</code>, and if it is, adds the markers to that layer.</p>
  
  <pre><code>$rootScope.on('newMarkers',markers)-&gt;
    type = *fn to find type*
    if mapFactory.currentLayers[type]?.active
       mapFactory.addLayer(markers, type)
  )
  </code></pre>
  
  <p>I don't think building in logic to see whether it's the <em>first</em> time a marker is being added to that layer makes sense, and would rather create an empty layer and add data to it after. I know you can do this with the <code>L.geoJson</code> type, but this layer is made entirely of plain <code>markers</code>. Any suggestions</p>