Fix warning of LW and OnTileRender OnValidate call

ScriptableRenderPipeline/LightweightPipeline/LWRP/Data/LightweightPipelineAsset.cs

             return new LightweightPipeline(this);
         }
 
-        void OnValidate()
-        {
-            DestroyCreatedInstances();
-        }
-
         private Material GetMaterial(DefaultMaterialType materialType)
         {
 #if UNITY_EDITOR

TestbedPipelines/OnTileDeferredPipeline/OnTileDeferredRenderPipeline.cs

 
 		private Material m_BlitMaterial;
 
-		private void OnValidate()
+		protected override void OnValidate()
-			Build();
+            base.OnValidate();
+            Build();
 		}
 
 		public void Cleanup()