protect call to glDeleteSamplers

Otherwise, it'd be possible to generate evil commands from a rouge
guest-driver that can crash the VM.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/vrend_renderer.c

@@ -1354,6 +1354,7 @@ static void vrend_destroy_sampler_state_object(void *obj_ptr)
 {
    struct vrend_sampler_state *state = obj_ptr;
 
+   if (vrend_state.have_samplers)
       glDeleteSamplers(1, &state->id);
    FREE(state);
 }