title: Leaflet: Circle behaving different from CircleMarker
body: <p>In the documentation for Leaflet here: <a href="http://leafletjs.com/reference-1.2.0.html#circlemarker" rel="nofollow noreferrer">http://leafletjs.com/reference-1.2.0.html#circlemarker</a> it says that CircleMaker extends Circle, and that it is the same thing, except the radius is specified in pixels rather than in meters, so that the circles stay constant size even if you zoom the map.</p>
  
  <p>I do however need Circles, because I am trying to draw 100m radius circles on a map. To do this, I use the following code:</p>
  
  <pre><code>var geojsonLayer = new L.GeoJSON(null,{
  pointToLayer: function (latlng){
      return new L.CircleMarker(latlng, {
          radius: 5,
          fillColor: "#ff7800",
          color: "#000",
          weight: 1,
          opacity: 1,
          fillOpacity: 0.8,
      });
  }});
  
  map.addLayer(osm);
  map.addLayer(geojsonLayer);
  geojsonLayer.addGeoJSON(jsonExample);
  </code></pre>
  
  <p>This works perfectly, however, if I change the code to use "Circle" instead of CircleMaker the entire map fails to load, and I get a javascript error:</p>
  
  <pre><code>Error: Error: Invalid LatLng object: (56.229917, NaN)
  </code></pre>
  
  <p>I can fix this by pre-filtering the geojson to remove those points which lack both latitude and longitude, but I'm confused: Circle and CircleMaker both specify that they take a LatLng-object as the specification of the center-point, I don't get how a certain LatLng object can be valid as centre-point for a CircleMarker, but invalid if used as the centerpoint for a Circle.</p>
  
  <p>Am I overlooking something obvious, or is this just a weakness and/or bug in Leaflet that I'll just have to work around ?</p>