[8.x.x] backport of #1898 null ref in cam prefab

com.unity.render-pipelines.universal/CHANGELOG.md

@@ -28,6 +28,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed Missing camera cannot be removed after scene is saved by removing the Missing camera label. [case 1252255](https://issuetracker.unity3d.com/issues/universal-rp-missing-camera-cannot-be-removed-from-camera-stack-after-scene-is-saved)
 - Fixed MissingReferenceException when removing Missing camera from camera stack by removing Missing camera label. [case 1252263](https://issuetracker.unity3d.com/issues/universal-rp-missingreferenceexception-errors-when-removing-missing-camera-from-stack)
 - Fixed a memory leak in Scriptable Renderer Data Editor.
+- Fixed an issue that caused a null reference when deleting camera component in a prefab. [case 1244430](https://issuetracker.unity3d.com/issues/urp-argumentnullexception-error-is-thrown-on-removing-camera-component-from-camera-prefab)
 
 ## [8.2.0] - 2020-07-08
 

com.unity.render-pipelines.universal/Editor/UniversalRenderPipelineCameraEditor.cs

@@ -1092,13 +1092,28 @@ public void RemoveComponent(Camera camera, IEnumerable<Component> dependencies)
                 return;
             }
 
-            Undo.SetCurrentGroupName("Remove Universal Camera");
-            var additionalCameraData = camera.GetComponent<UniversalAdditionalCameraData>();
-            if (additionalCameraData)
+            var isAssetEditing = EditorUtility.IsPersistent(camera);
+            try
             {
-                Undo.DestroyObjectImmediate(additionalCameraData);
+                if (isAssetEditing)
+                {
+                    AssetDatabase.StartAssetEditing();
+                }
+                Undo.SetCurrentGroupName("Remove Universal Camera");
+                var additionalCameraData = camera.GetComponent<UniversalAdditionalCameraData>();
+                if (additionalCameraData != null)
+                {
+                    Undo.DestroyObjectImmediate(additionalCameraData);
+                }
+                Undo.DestroyObjectImmediate(camera);
+            }
+            finally
+            {
+                if (isAssetEditing)
+                {
+                    AssetDatabase.StopAssetEditing();
+                }
             }
-            Undo.DestroyObjectImmediate(camera);
         }
     }
 }