Problem with OgreNewt demo (Demo 02 - Joints)

Hello,
I'm just a beginner in Ogre and in OgreNewt so when I want to try something, I open demos and samples at first. When I got to second (Demo 2 - Joints), I finished. After I compiled the code and run it, it crashed. So I tried to debug and I found that the exception comes from this code:

/* using the new "SceneParser" TreeCollision primitive. this will automatically parse an entire tree of SceneNodes (parsing all children), and add collision for all meshes in the tree. */
OgreNewt::CollisionPrimitives::TreeCollisionSceneParser* stat_col = new OgreNewt::CollisionPrimitives::TreeCollisionSceneParser( mWorld );
// here the problem comes from
stat_col->parseScene( floornode, true );
OgreNewt::Body* bod = new OgreNewt::Body( mWorld, stat_col );
delete stat_col;

So I looked at the code and I found that the exceptions always comes from this code:

while (child_it.hasMoreElements())
{ //...

which is in OgreNewt_CollisionPrimitives.cpp at line 522 in TreeCollisionSceneParser::_parseNode function.
Does anyone have the same problem and fixed it or knows solution?