Fix T79692: Full copy of scene makes Blender freeze if there is content directly in the master collection.

Old and new collections are the same data in Master collection case
here, so we cannot consider the `gobject` listbase of `collection_old`
as always immutable.

1 files changed, 3 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/collection.c b/source/blender/blenkernel/intern/collection.c
index 6118325c231..5c618c8e9ce 100644
--- a/source/blender/blenkernel/intern/collection.c
+++ b/source/blender/blenkernel/intern/collection.c
@@ -408,9 +408,9 @@ static Collection *collection_duplicate_recursive(Main *bmain,
   }
 
   if (do_objects) {
-    /* We can loop on collection_old's objects, that list is currently identical the collection_new
-     * objects, and won't be changed here. */
-    LISTBASE_FOREACH (CollectionObject *, cob, &collection_old->gobject) {
+    /* We can loop on collection_old's objects, but have to consider it mutable because with master
+     * collections collection_old and collection_new are the same data here. */
+    LISTBASE_FOREACH_MUTABLE (CollectionObject *, cob, &collection_old->gobject) {
       Object *ob_old = cob->ob;
       Object *ob_new = (Object *)ob_old->id.newid;