QmlEditorWidgets: Compile with QT_NO_CAST_FROM_ASCII

Change-Id: I84ed6dca71621a4e790f5aff0ad25339fb9e8772
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>

src/libs/qmleditorwidgets/gradientline.cpp

@@ -62,7 +62,7 @@ static inline QColor invertColor(const QColor color)
 GradientLine::GradientLine(QWidget *parent) :
         QWidget(parent),
         m_activeColor(Qt::black),
-        m_gradientName("gradient"),
+        m_gradientName(QLatin1String("gradient")),
         m_colorIndex(0),
         m_dragActive(false),
         m_yOffset(0),