Handle cases where fragdata or attrib location idx is -1
Handle cases where fragdata or attrib location idx is -1

* This can happen when we're copying from a source program to a dest
  program where the source is non-separable and had an attribute
  optimised out entirely, but the destination is separable and so still
  wants that attribute. In this case it'll come out in the wash and
  we can just skip it.

Lssikkes/renderdoc,TurtleRockStudios/renderdoc_public,TurtleRockStudios/renderdoc_public,baldurk/renderdoc,cgmb/renderdoc,Lssikkes/renderdoc,victor-moya/renderdoc,Velro/renderdoc,moradin/renderdoc,Velro/renderdoc,Anteru/renderdoc,cgmb/renderdoc,TurtleRockStudios/renderdoc_public,Yours3lf/renderdoc,Velro/renderdoc,etnlGD/renderdoc,michaelrgb/renderdoc,Anteru/renderdoc,moradin/renderdoc,Yours3lf/renderdoc,adrianbu/renderdoc,moradin/renderdoc,TurtleRockStudios/renderdoc_public,googlestadia/renderdoc,victor-moya/renderdoc,baldurk/renderdoc,etnlGD/renderdoc,adrianbu/renderdoc,googlestadia/renderdoc,TurtleRockStudios/renderdoc_public,michaelrgb/renderdoc,cgmb/renderdoc,Yours3lf/renderdoc,michaelrgb/renderdoc,Lssikkes/renderdoc,googlestadia/renderdoc,moradin/renderdoc,Yours3lf/renderdoc,michaelrgb/renderdoc,Anteru/renderdoc,baldurk/renderdoc,moradin/renderdoc,googlestadia/renderdoc,adrianbu/renderdoc,michaelrgb/renderdoc,cgmb/renderdoc,adrianbu/renderdoc,victor-moya/renderdoc,adrianbu/renderdoc,Lssikkes/renderdoc,cgmb/renderdoc,etnlGD/renderdoc,Zorro666/renderdoc,Yours3lf/renderdoc,Zorro666/renderdoc,googlestadia/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,Anteru/renderdoc,etnlGD/renderdoc,moradin/renderdoc,googlestadia/renderdoc,Anteru/renderdoc,etnlGD/renderdoc,victor-moya/renderdoc,Anteru/renderdoc,Velro/renderdoc,victor-moya/renderdoc,Lssikkes/renderdoc,Velro/renderdoc,Yours3lf/renderdoc,etnlGD/renderdoc,Velro/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,Anteru/renderdoc,Lssikkes/renderdoc,baldurk/renderdoc,TurtleRockStudios/renderdoc_public,victor-moya/renderdoc,Zorro666/renderdoc,adrianbu/renderdoc