Avoid failure of file writing if face colors or face normals are requested for PLY files. We just skip these options at this point.
Avoid failure of file writing if face colors or face normals are requested for PLY files. We just skip these options at this point.

git-svn-id: e0b5bbb11d0e9fdbbfcabba14dc32ad5d6b235bd@347 fdac6126-5c0c-442c-9429-916003d36597

svn2github/OpenMesh2,svn2github/OpenMesh2,svn2github/OpenMesh2,svn2github/OpenMesh2,svn2github/OpenMesh2,svn2github/OpenMesh4,svn2github/OpenMesh4,svn2github/OpenMesh4,svn2github/OpenMesh4,svn2github/OpenMesh4