Add if ( onError ) check in GLTFLoader

examples/js/loaders/GLTFLoader.js

@@ -84,7 +84,7 @@ THREE.GLTFLoader = ( function () {
 
 					} catch ( error ) {
 
-						onError( error );
+						if ( onError ) onError( error );
 						return;
 
 					}
@@ -103,7 +103,7 @@ THREE.GLTFLoader = ( function () {
 
 			if ( json.asset === undefined || json.asset.version[ 0 ] < 2 ) {
 
-				onError( new Error( 'THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported.' ) );
+				if ( onError ) onError( new Error( 'THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported.' ) );
 				return;
 
 			}