Add missing alpha value option for colour ramps

Author: NathanW2

src/gui/symbology-ng/qgsvectorgradientcolorrampv2dialog.cpp

@@ -268,7 +268,8 @@ void QgsVectorGradientColorRampV2Dialog::stopDoubleClicked( QTreeWidgetItem* ite
       mCurrentItem = item;
       color = QgsColorDialog::getLiveColor(
                 item->data( 0, StopColorRole ).value<QColor>(),
-                this, SLOT( setItemStopColor( const QColor& ) ), this );
+              this, SLOT( setItemStopColor( const QColor& ) ),
+              this, tr("Edit Stop Color"), QColorDialog::ShowAlphaChannel );
       mCurrentItem = 0;
     }
     else