Fix #11703 and #11704

Do not create a layer node if the passed layer cannot be used (not in registry)

Author: wonder-sk

src/core/layertree/qgslayertreegroup.cpp

@@ -17,6 +17,8 @@
 
 #include "qgslayertree.h"
 #include "qgslayertreeutils.h"
+#include "qgsmaplayer.h"
+#include "qgsmaplayerregistry.h"
 
 #include <QDomElement>
 #include <QStringList>
@@ -57,13 +59,19 @@ QgsLayerTreeGroup* QgsLayerTreeGroup::addGroup( const QString &name )
 
 QgsLayerTreeLayer*QgsLayerTreeGroup::insertLayer( int index, QgsMapLayer* layer )
 {
+  if ( !layer || QgsMapLayerRegistry::instance()->mapLayer( layer->id() ) != layer )
+    return 0;
+
   QgsLayerTreeLayer* ll = new QgsLayerTreeLayer( layer );
   insertChildNode( index, ll );
   return ll;
 }
 
 QgsLayerTreeLayer* QgsLayerTreeGroup::addLayer( QgsMapLayer* layer )
 {
+  if ( !layer || QgsMapLayerRegistry::instance()->mapLayer( layer->id() ) != layer )
+    return 0;
+
   QgsLayerTreeLayer* ll = new QgsLayerTreeLayer( layer );
   addChildNode( ll );
   return ll;