Three.js OBJ + MTLLoader causing TypeError "ambientLightColor is undefined"

Question

I'm kind of new to Three JS, but I know the basics of it.

Now I'm having following problem in my code using ThreeJS's MTL and OBJLoader. Object itself is perfectly loaded and rendered to the scene. However, the problem is after object is added to scene I'm getting the following errors:

TypeError: k.ambientLightColor is undefined, three.min.js (line 136, col 35)
TypeError: m.ambientLightColor is undefined, three.min.js (line 139, col 22)

And there's new error everytime when I hover over the scene.

Basically this freezes the whole application, and I'm not able to add new objects to scene while the application is running, that I should be able to do in my application.

My OBJ+MTLLoader looks like this:

var mtlLoader = new THREE.MTLLoader();
mtlLoader.setPath('objects/buildings/');
mtlLoader.load('Greenbuilding.mtl', function(materials) {
     materials.preload();
     var objLoader = new THREE.OBJLoader();
     objLoader.setMaterials(materials);
     objLoader.setPath('objects/buildings/');
     objLoader.load('Greenbuilding.obj', function(object) {
        object.position.set(0,0,0);
        objects.push(object);
        scene.add(object);
     }, onProgress, onError);
    });

I've tried to use OBJLoader only, and no problem occurred then, which confirms my doubts, that there's something wrong when using MTLLoader.