Make sure the QDockAreaLayoutInfo item_list is detached when we are going to modify it

This can lead to situations in which the gap item ends up in the
saved state
'subinfo' is owned by the item, but the const-ness is not transferred to
the pointer. So calling a non const function (unplug) that changes the
subinfo changes it in the original list as well.
This is a problem because that list might be shared with the saved state.

Change-Id: I90a5faafea5958043db610a84c069494f2e48137
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Jocelyn Turcotte (Woboq GmbH) <jturcotte@woboq.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/widgets/widgets/qdockarealayout.cpp b/src/widgets/widgets/qdockarealayout.cpp
index bc2259ce90..8054c8aa46 100644
--- a/src/widgets/widgets/qdockarealayout.cpp
+++ b/src/widgets/widgets/qdockarealayout.cpp
@@ -1018,7 +1018,7 @@ QLayoutItem *QDockAreaLayoutInfo::plug(const QList<int> &path)
         index = -index - 1;
 
     if (path.count() > 1) {
-        const QDockAreaLayoutItem &item = item_list.at(index);
+        QDockAreaLayoutItem &item = item_list[index];
         Q_ASSERT(item.subinfo != 0);
         return item.subinfo->plug(path.mid(1));
     }
@@ -1064,7 +1064,7 @@ QLayoutItem *QDockAreaLayoutInfo::unplug(const QList<int> &path)
 
     const int index = path.first();
     if (path.count() > 1) {
-        const QDockAreaLayoutItem &item = item_list.at(index);
+        QDockAreaLayoutItem &item = item_list[index];
         Q_ASSERT(item.subinfo != 0);
         return item.subinfo->unplug(path.mid(1));
     }