message: Don't look for binding clashes with a NULL UAV
diff: @@ -1341,6 +1341,9 @@ bool D3D11RenderState::ValidOutputMerger(ID3D11RenderTargetView **RTs, ID3D11Dep
  for(int i = 0; valid && i < numUAVs; i++)
  {
  + if(uavRanges[i].IsNull())
  + continue;
  +
  // don't have to check RTVs, that's the reflection of the above check
  // does it match depth?
  