st/mesa: set the vbuffer to NULL if we are skipping it
st/mesa: set the vbuffer to NULL if we are skipping it

If we skip a vbuffer we need to make sure we NULL out
the contents, otherwise when it gets passed to the driver
it will get confused.

This was hit by:
GL41-CTS.gpu_shader_fp64.varyings

Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler