fix error running ED_view3d_project_float_v3_m4 on 2d vec (thanks Sergey for pointing out!), also remove redundant vector copy in knife project.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56450 954f8c5b-7b00-dc11-b283-0030488c597c