message: gltfio: fix vertex attribute type mismatch.
  Vulkan complains if a pipeline declares an integer vec2 attribute but
  the shader consumes it as "vec2" rather than "ivec2". gltfio was doing
  this when supplying dummy texture coordinates.
  This fixes one of the two bugs reported in
diff: @@ -639,10 +639,12 @@ bool FAssetLoader::createPrimitive(const cgltf_primitive* inPrim, Primitive* out
  if (!hasUv0) {
  needsDummyData = true;
  vbb.attribute(VertexAttribute::UV0, slot, VertexBuffer::AttributeType::USHORT2);
  + vbb.normalized(VertexAttribute::UV0);
  }
  if (!hasUv1) {
  needsDummyData = true;
  vbb.attribute(VertexAttribute::UV1, slot, VertexBuffer::AttributeType::USHORT2);
  + vbb.normalized(VertexAttribute::UV1);
  }
  if (!hasVertexColor) {
  needsDummyData = true;
  @@ -654,11 +656,13 @@ bool FAssetLoader::createPrimitive(const cgltf_primitive* inPrim, Primitive* out
  if (!hasUv0 && numUvSets > 0) {
  needsDummyData = true;
  vbb.attribute(VertexAttribute::UV0, slot, VertexBuffer::AttributeType::USHORT2);
  + vbb.normalized(VertexAttribute::UV0);
  slog.w << "Missing UV0 data in " << name << io::endl;
  }
  if (!hasUv1 && numUvSets > 1) {
  needsDummyData = true;
  vbb.attribute(VertexAttribute::UV1, slot, VertexBuffer::AttributeType::USHORT2);
  + vbb.normalized(VertexAttribute::UV1);
  slog.w << "Missing UV1 data in " << name << io::endl;
  }
  }
  