Fix raycaster warning

Author: diarmidmackenzie

examples/checkpoints/index.html

@@ -20,6 +20,7 @@
                   position="0 1.6 0"
                   look-controls="pointerLockEnabled: true">
           <a-entity cursor
+                    raycaster="objects:[checkpoint]"
                     position="0 0 -1"
                     geometry="primitive: ring; radiusInner: 0.02; radiusOuter: 0.03;"
                     material="color: #CCC; shader: flat;"></a-entity>