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 <marek.olsak@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/mesa/state_tracker/st_atom_array.c

@@ -567,8 +567,12 @@ setup_non_interleaved_attribs(struct st_context *st,
       unsigned src_format;
 
       array = get_client_array(vp, arrays, attr);
-      if (!array)
+      if (!array) {
+         vbuffer[attr].buffer = NULL;
+         vbuffer[attr].user_buffer = NULL;
+         vbuffer[attr].buffer_offset = 0;
          continue;
+      }
 
       stride = array->StrideB;
       bufobj = array->BufferObj;