If a primitive is added with missing vertices, this will shift all
the vertices and produce incorrect rendering.
In issue #5786 the app uses GL_LINE_STRIPS with a single vertex.
Adding extra vertices can make the initial estimation for the index
buffer size incorrect, so this buffer can now be growed if needed.
Fixes: ac3d4c7635 ("vbo/dlist: convert LINE_STRIPS to LINES")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5786
Acked-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14476>
(cherry picked from commit dcbf2423d2)