Calling d2d_outline_vertex_set(x, y, 0, 0, 0, 0) causes a normalize() to
be invoked with a zero vector in the vertex shader
vs_code_bezier_outline. This gives rise to an undefinite result, that in
some cases causes the join triangles to be dropped.

Tested on Debian unstable.
Signed-off-by: Giovanni Mascellani <g.mascellani@gmail.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>