invalid output of merged ao_met_rough when no ao supplied

[rdpeake]

if you supply a model which does not have an occlusion map, but do have met and rough - the combined result at

FBX2glTF/src/gltf/Raw2Gltf.cpp

Line 280 in 4b50143

 aoMetRoughTex = textureBuilder.combine( 

seems to produce an invalid output for the ao_met_rough file

[rdpeake]

suggest changing

FBX2glTF/src/gltf/Raw2Gltf.cpp

Line 289 in 4b50143

 const float occlusion = (*pixels[0])[0]; 

with

const float occlusion = (*pixels[0])[0] * (hasOcclusionMap ? 1 : 0);

or use the props object if that is supported for occlusion in place of the ending 0

[rdpeake]

This turned out to be invalid due to a difference in what input files i was actually using