BaseTabular density model gets wrong result if the initial point and the final point of trajectory has the same height

The current BaseTabular density model does not support for the situation where curvature effect is strong.

For example, in the following geometry, the initial point of trajectory and the final point of trajectory have the same height compare to the center of sphere. In that case, the BaseTabular::getIntegratedGrammage(BaseTrajectory &) will return 0.