fix issue where render would not be recreated.

Assets/ScriptableRenderLoop/HDRenderPipeline/Sky/SkyManager.cs

                     m_Renderer = null;
                 }
 
-                if (value == null)
-                    return;
-
-                m_Renderer = value.GetRenderer();
+
+                if (value != null)
+                    m_Renderer = value.GetRenderer();
             }
             get { return m_SkyParameters; }
         }