Remove aiCreateAndRegisterDefaultMaterial, it's completely wrong

code/Importer.cpp

@@ -178,7 +178,6 @@ Importer::~Importer()
 {
     // Delete all import plugins
 	DeleteImporterInstanceList(pimpl->mImporter);
-    aiReleaseDefaultMaterial();
 
     // Delete all post-processing plug-ins
     for( unsigned int a = 0; a < pimpl->mPostProcessingSteps.size(); a++)
@@ -385,7 +384,6 @@ void Importer::FreeScene( )
 {
     ASSIMP_BEGIN_EXCEPTION_REGION();
 
-    aiReleaseDefaultMaterial();
     delete pimpl->mScene;
     pimpl->mScene = NULL;