Revert "Fix warning about null pointer being passed to memcpy"

This reverts commit e295ae2c. The method is used to fill a Transformation3D from data cached in the navigation index table, which is stored in unaligned memory to be more compact, so may produce crashes - as we observe when porting the Retracer example in AdePT using VecGeom master. In case this produces warnings due to passing null pointer to memcpy as the original commit reported, we need to reproduce and fix the reason of that.