Clear WMS preview image

src/providers/wms/qgswmsprovider.cpp

@@ -616,6 +616,7 @@ static void _drawDebugRect( QPainter& p, const QRectF& rect, const QColor& color
 QImage *QgsWmsProvider::draw( QgsRectangle const & viewExtent, int pixelWidth, int pixelHeight, QgsRasterBlockFeedback* feedback )
 {
   QImage* image = new QImage( pixelWidth, pixelHeight, QImage::Format_ARGB32 );
+  image->fill( 0 );
 
   if ( QgsApplication::instance()->thread() == QThread::currentThread() )
   {
@@ -624,9 +625,6 @@ QImage *QgsWmsProvider::draw( QgsRectangle const & viewExtent, int pixelWidth, i
   }
 
   // compose the URL query string for the WMS server.
-
-  image->fill( 0 );
-
   if ( !mSettings.mTiled && mSettings.mMaxWidth == 0 && mSettings.mMaxHeight == 0 )
   {
     QUrl url = createRequestUrlWMS( viewExtent, pixelWidth, pixelHeight );