Fix fot ROOT-9938. Bug in navigation of TGeoPgon when ray was hitting the Z axis.
Fix fot ROOT-9938. Bug in navigation of TGeoPgon when ray was hitting the Z axis.

karies/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,olifre/root,karies/root,karies/root,karies/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,olifre/root,olifre/root,karies/root