Don't access data in moved-from object

It's undefined behavior, esp since we leave it to the compiler to
implement a move constructor for the ButtonInfo struct. So read the data
that we need first.

Fixes static analyzer warning
de76eedae524c86f89d6369c0f5af8c7.

Pick-to: 6.1
Change-Id: I8fc458b7e9ba8904ec7a3b1c26aac0628e336ea2
Reviewed-by: Doris Verria <doris.verria@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/widgets/styles/qstylesheetstyle.cpp

@@ -863,9 +863,9 @@ QHash<QStyle::SubControl, QRect> QStyleSheetStyle::titleBarLayout(const QWidget
             info.rule = subRule;
             info.offset = offsets[where];
             info.where = where;
-            infos.append(std::move(info));
-
             offsets[where] += info.width;
+
+            infos.append(std::move(info));
         }
     }