Fix bug in dealing with zero forward tangential velocity.
Fix bug in dealing with zero forward tangential velocity.

dariomangoni/chrono,dariomangoni/chrono,andrewseidl/chrono,Bryan-Peterson/chrono,tjolsen/chrono,Bryan-Peterson/chrono,tjolsen/chrono,armanpazouki/chrono,andrewseidl/chrono,armanpazouki/chrono,dariomangoni/chrono,armanpazouki/chrono,jcmadsen/chrono,Bryan-Peterson/chrono,rserban/chrono,jcmadsen/chrono,amelmquist/chrono,projectchrono/chrono,Bryan-Peterson/chrono,tjolsen/chrono,amelmquist/chrono,jcmadsen/chrono,jcmadsen/chrono,projectchrono/chrono,armanpazouki/chrono,andrewseidl/chrono,Milad-Rakhsha/chrono,rserban/chrono,rserban/chrono,andrewseidl/chrono,jcmadsen/chrono,rserban/chrono,Bryan-Peterson/chrono,Milad-Rakhsha/chrono,andrewseidl/chrono,armanpazouki/chrono,dariomangoni/chrono,Milad-Rakhsha/chrono,projectchrono/chrono,jcmadsen/chrono,rserban/chrono,jcmadsen/chrono,Milad-Rakhsha/chrono,dariomangoni/chrono,dariomangoni/chrono,projectchrono/chrono,amelmquist/chrono,rserban/chrono,projectchrono/chrono,projectchrono/chrono,Milad-Rakhsha/chrono,tjolsen/chrono,armanpazouki/chrono,amelmquist/chrono,Milad-Rakhsha/chrono,rserban/chrono,amelmquist/chrono,amelmquist/chrono,tjolsen/chrono