Fix bug for planar meshes

Former-commit-id: 07068f44df5a3917109c60455d04a754ef2290c0

include/igl/comiso/miq.cpp

@@ -488,7 +488,7 @@ IGL_INLINE void igl::comiso::VertexIndexing<DerivedV, DerivedF>::InitSeamInfo()
   {
       int f0 = EF(e,0);
       int f1 = EF(e,1);
-      if (f1 == -1)
+      if (f1 == -1 || f0 == -1)
         continue;
 
       int k=0;