Initialize member variable

Change-Id: I165c267b87dc201ed4970d50e39ff7421cbef35f
Reviewed-on: http://codereview.qt.nokia.com/3981
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

src/gui/kernel/qguiapplication.cpp

@@ -172,7 +172,8 @@ QGuiApplication::~QGuiApplication()
 }
 
 QGuiApplicationPrivate::QGuiApplicationPrivate(int &argc, char **argv, int flags)
-    : QCoreApplicationPrivate(argc, argv, flags)
+    : QCoreApplicationPrivate(argc, argv, flags),
+      styleHints(0)
 {
     self = this;
 }