Fix T53052: ID decrement error when deleting a scene, either python or GUI.

User count of scenes was inconsistant, screens only have 'user_one' kind
of owning over scenes, which means they shall never increment or
decrement their real user count. And usually, scenes have no real user
at all.

2 files changed, 7 insertions, 2 deletions

diff --git a/source/blender/blenkernel/intern/scene.c b/source/blender/blenkernel/intern/scene.c
index d32a3a293fd..4526477cad9 100644
--- a/source/blender/blenkernel/intern/scene.c
+++ b/source/blender/blenkernel/intern/scene.c
@@ -290,7 +290,7 @@ Scene *BKE_scene_copy(Main *bmain, Scene *sce, int type)
 		ListBase rl, rv;
 
 		sce_copy = BKE_scene_add(bmain, sce->id.name + 2);
-		
+
 		rl = sce_copy->r.layers;
 		rv = sce_copy->r.views;
 		curvemapping_free_data(&sce_copy->r.mblur_shutter_curve);
@@ -387,6 +387,8 @@ Scene *BKE_scene_copy(Main *bmain, Scene *sce, int type)
 	}
 	else {
 		BKE_id_copy_ex(bmain, (ID *)sce, (ID **)&sce_copy, LIB_ID_COPY_ACTIONS, false);
+		id_us_min(&sce_copy->id);
+		id_us_ensure_real(&sce_copy->id);
 
 		/* Extra actions, most notably SCE_FULL_COPY also duplicates several 'children' datablocks... */
 
diff --git a/source/blender/editors/screen/screen_edit.c b/source/blender/editors/screen/screen_edit.c
index 71b00a0a7c6..c99e452b755 100644
--- a/source/blender/editors/screen/screen_edit.c
+++ b/source/blender/editors/screen/screen_edit.c
@@ -1763,7 +1763,10 @@ bool ED_screen_delete_scene(bContext *C, Scene *scene)
 
 	BKE_libblock_remap(bmain, scene, newscene, ID_REMAP_SKIP_INDIRECT_USAGE | ID_REMAP_SKIP_NEVER_NULL_USAGE);
 
-	BKE_libblock_free_us(bmain, scene);
+	id_us_clear_real(&scene->id);
+	if (scene->id.us == 0) {
+		BKE_libblock_free(bmain, scene);
+	}
 
 	return true;
 }