mesa: stop using _Depth, _StencilBuffer fields in _mesa_BlitFramebufferEXT()

We're just looking at the depth/stencil renderbuffers to do error
checking.  We don't need to look at the depth/stencil wrappers to do
that.  Also, remove pointless readRb = depthRb = NULL assignments.

Reviewed-by: Eric Anholt <eric@anholt.net>
1 file changed