Fix build with Qt4

broke with 6e432b9d4e99ca233fb687be142b8782342f41d7

Change-Id: I67bda87a4fd0f9e0c2305843ae732b3bb66bf0c8
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>

src/libs/qtcomponents/styleitem/qstyleitem.cpp

@@ -404,7 +404,9 @@ void QStyleItem::initStyleOption()
         m_styleoption = new QStyleOption();
 
     m_styleoption->rect = QRect(m_paintMargins, m_paintMargins, width() - 2* m_paintMargins, height() - 2 * m_paintMargins);
+#if QT_VERSION >= 0x050000
     m_styleoption->styleObject = this;
+#endif
 
     if (isEnabled())
         m_styleoption->state |= QStyle::State_Enabled;