fix memory leak when rl::sg::ode::Shape is destroyed

[ahgnuoy]

I discovered a memory leak when destroying rl::sg::ode::Scene. Upon investigation, I found that the ::dTriMeshDataID created during the creation of rl::sg::ode::Shape was not being destroyed. To correct this, I modified the code as follows.

[rickertm]

Thank you very much for pointing this out. Could you please initialize the data member to nullptr in the member initializer list and move it to private? Without the initialization, this creates an exception for the other shape types and it should not be accessible publicly.

[rickertm]

Thank you for adding the initialization, the tests work correctly now. Could you please update the data member to use alphabetical order within the private section?