Use QScopedPointer to store decoration object

This simplifies memory management.

(cherry picked from commit 637d914f)

src/abstract_client.cpp

@@ -2362,14 +2362,13 @@ void AbstractClient::createDecoration(const QRect &oldGeometry)
 
 void AbstractClient::destroyDecoration()
 {
-    delete m_decoration.decoration;
     setDecoration(nullptr);
     m_decoration.inputRegion = QRegion();
 }
 
 void AbstractClient::setDecoration(KDecoration2::Decoration *decoration)
 {
-    m_decoration.decoration = decoration;
+    m_decoration.decoration.reset(decoration);
     Q_EMIT decorationChanged();
 }
 

src/abstract_client.h

@@ -742,10 +742,10 @@ public:
 
     // decoration related
     KDecoration2::Decoration *decoration() {
-        return m_decoration.decoration;
+        return m_decoration.decoration.data();
     }
     const KDecoration2::Decoration *decoration() const {
-        return m_decoration.decoration;
+        return m_decoration.decoration.data();
     }
     bool isDecorated() const {
         return m_decoration.decoration != nullptr;
@@ -1323,7 +1323,7 @@ private:
     } m_interactiveMoveResize;
 
     struct {
-        KDecoration2::Decoration *decoration = nullptr;
+        QScopedPointer<KDecoration2::Decoration> decoration;
         QPointer<Decoration::DecoratedClientImpl> client;
         QElapsedTimer doubleClickTimer;
         QRegion inputRegion;