LightShadow: Fix isShadowCamera flag.

Author: Mugen87

src/lights/LightShadow.js

@@ -114,6 +114,7 @@ class LightShadow {
 	copy( source ) {
 
 		this.camera = source.camera.clone();
+		this.camera.isShadowCamera = true;
 
 		this.intensity = source.intensity;