[decorations] Delay closeWindow to next event cycle

Once again our famous "closing glxgears crashes Aurorae".

BUG: 346857
FIXED-IN: 5.4.3
REVIEW: 125704

decorations/decoratedclient.cpp

@@ -163,10 +163,14 @@ DELEGATE(requestToggleKeepBelow, KeepBelowOp)
 
 DELEGATE(requestContextHelp, showContextHelp)
 DELEGATE(requestMinimize, minimize)
-DELEGATE(requestClose, closeWindow)
 
 #undef DELEGATE
 
+void DecoratedClientImpl::requestClose()
+{
+    QMetaObject::invokeMethod(m_client, "closeWindow", Qt::QueuedConnection);
+}
+
 QColor DecoratedClientImpl::color(KDecoration2::ColorGroup group, KDecoration2::ColorRole role) const
 {
     auto dp = m_client->decorationPalette();