Fix some minor coverity warnings

Author: nyalldawson

src/analysis/raster/qgsalignraster.cpp

@@ -477,7 +477,7 @@ bool QgsAlignRaster::createAndWarp( const Item& raster )
     psWarpOptions->panDstBands[i] = i + 1;
   }
 
-  psWarpOptions->eResampleAlg = ( GDALResampleAlg ) raster.resampleMethod;
+  psWarpOptions->eResampleAlg = static_cast< GDALResampleAlg >( raster.resampleMethod );
 
   // our progress function
   psWarpOptions->pfnProgress = _progress;

src/app/qgsapplayertreeviewmenuprovider.cpp

@@ -101,7 +101,7 @@ QMenu* QgsAppLayerTreeViewMenuProvider::createContextMenu()
       // duplicate layer
       QAction* duplicateLayersAction = menu->addAction( QgsApplication::getThemeIcon( "/mActionDuplicateLayer.svg" ), tr( "&Duplicate" ), QgisApp::instance(), SLOT( duplicateLayers() ) );
 
-      if ( layer->isSpatial() )
+      if ( layer && layer->isSpatial() )
       {
         // set layer scale visibility
         menu->addAction( tr( "&Set Layer Scale Visibility" ), QgisApp::instance(), SLOT( setLayerScaleVisibility() ) );

src/gui/qgscomposerview.cpp

@@ -372,7 +372,7 @@ void QgsComposerView::mousePressEvent( QMouseEvent* e )
           if (( item->type() == QgsComposerItem::ComposerPolygon
                 || item->type() == QgsComposerItem::ComposerPolyline ) )
           {
-            QgsComposerNodesItem* itemP = dynamic_cast<QgsComposerNodesItem *>( item );
+            QgsComposerNodesItem* itemP = static_cast<QgsComposerNodesItem *>( item );
             int index = itemP->nodeAtPosition( scenePoint );
             if ( index != -1 )
             {