[7.x.x backport] Follow references when deleting unloading unused assets on shader graph save (case 1230996)

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -40,6 +40,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fix for range compression factor for probes going negative (now clamped to positive values).
 - Fixed path validation when creating new volume profile (case 1229933)
 - Fixed various object leaks in HDRP.
+- Fix for assertion triggering sometimes when saving a newly created lit shader graph (case 1230996)
 
 ### Changed
 - Rejecting history for ray traced reflections based on a threshold evaluated on the neighborhood of the sampled history.

com.unity.render-pipelines.high-definition/Editor/AssetProcessors/ShaderGraphMaterialsUpdater.cs

@@ -55,13 +55,13 @@ static void OnShaderGraphSaved(Shader shader, object saveContext)
 
                     // Free the materials every 200 iterations, on big project loading all materials in memory can lead to a crash
                     if ((i % 200 == 0) && i != 0)
-                        EditorUtility.UnloadUnusedAssetsImmediate(false);
+                        EditorUtility.UnloadUnusedAssetsImmediate(true);
                 }
             }
             finally
             {
                 EditorUtility.ClearProgressBar();
-                EditorUtility.UnloadUnusedAssetsImmediate(false);
+                EditorUtility.UnloadUnusedAssetsImmediate(true);
             }
         }
     }