mesa: Fix VAO buffer object tracking.

When changing the attribute binding in the VAO we also need to
account for getting rid of non vbo bits from VertexAttribBufferMask.

Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/varray.c

@@ -168,6 +168,8 @@ vertex_attrib_binding(struct gl_context *ctx,
 
       if (_mesa_is_bufferobj(vao->BufferBinding[bindingIndex].BufferObj))
          vao->VertexAttribBufferMask |= array_bit;
+      else
+         vao->VertexAttribBufferMask &= ~array_bit;
 
       FLUSH_VERTICES(ctx, _NEW_ARRAY);