Coverity fixes, including regression in label point obstacle code

Author: nyalldawson

src/core/symbology-ng/qgsgeometrygeneratorsymbollayerv2.cpp

@@ -55,6 +55,7 @@ QgsGeometryGeneratorSymbolLayerV2::QgsGeometryGeneratorSymbolLayerV2( const QStr
     , mLineSymbol( nullptr )
     , mMarkerSymbol( nullptr )
     , mSymbol( nullptr )
+    , mSymbolType( QgsSymbolV2::Marker )
 {
 
 }

src/core/symbology-ng/qgssymbolv2.cpp

@@ -1291,7 +1291,7 @@ QRectF QgsMarkerSymbolV2::bounds( const QPointF& point, QgsRenderContext& contex
       if ( bound.isNull() )
         bound = symbolLayer->bounds( point, symbolContext );
       else
-        bound = symbolLayer->bounds( point, symbolContext );
+        bound = bound.united( symbolLayer->bounds( point, symbolContext ) );
     }
   }
   return bound;

src/gui/symbology-ng/qgssymbollayerv2widget.cpp

@@ -3091,6 +3091,7 @@ void QgsSvgGroupsModel::createTree( QStandardItem*& parentGroup )
 
 QgsGeometryGeneratorSymbolLayerWidget::QgsGeometryGeneratorSymbolLayerWidget( const QgsVectorLayer* vl, QWidget* parent )
     : QgsSymbolLayerV2Widget( parent, vl )
+    , mLayer( nullptr )
 {
   setupUi( this );
   modificationExpressionSelector->setLayer( const_cast<QgsVectorLayer*>( vl ) );