ObjectLoader: Fixed LineLoop dependency.

src/loaders/ObjectLoader.js

@@ -26,6 +26,7 @@ import { Group } from '../objects/Group';
 import { Sprite } from '../objects/Sprite';
 import { Points } from '../objects/Points';
 import { Line } from '../objects/Line';
+import { LineLoop } from '../objects/LineLoop';
 import { LineSegments } from '../objects/LineSegments';
 import { LOD } from '../objects/LOD';
 import { Mesh } from '../objects/Mesh';