[xembedsniproxy] Free windowAttributes in every case

The structure was only freed in case the XTest method was chosen.
But it should always be freed of course (as long as it isn't NULL).

Use a QScopedPointer instead to free it automatically when it goes out
of scope and to be more consistent with the rest of t

Differential Revision: https://phabricator.kde.org/D6389

xembed-sni-proxy/sniproxy.cpp

@@ -208,10 +208,9 @@ SNIProxy::SNIProxy(xcb_window_t wid, QObject* parent):
     //we query if the client selected button presses in the event mask
     //if the client does supports that we send directly, otherwise we'll use xtest
     auto waCookie = xcb_get_window_attributes(c, wid);
-    auto windowAttributes = xcb_get_window_attributes_reply(c, waCookie, nullptr);
+    QScopedPointer<xcb_get_window_attributes_reply_t, QScopedPointerPodDeleter> windowAttributes(xcb_get_window_attributes_reply(c, waCookie, nullptr));
     if (windowAttributes && ! (windowAttributes->all_event_masks & XCB_EVENT_MASK_BUTTON_PRESS)) {
         m_injectMode = XTest;
-        free(windowAttributes);
     }
 
     //there's no damage event for the first paint, and sometimes it's not drawn immediately