WebGLProgram: support cube uv refaction mapping

src/renderers/webgl/WebGLProgram.js

@@ -340,6 +340,7 @@ function generateEnvMapModeDefine( parameters ) {
 
 			case CubeRefractionMapping:
 			case EquirectangularRefractionMapping:
+			case CubeUVRefractionMapping:
 				envMapModeDefine = 'ENVMAP_MODE_REFRACTION';
 				break;