FromHoudiniGeometryConverter: Support for Houdini 17.5.
FromHoudiniGeometryConverter: Support for Houdini 17.5.

Since 17.5, Sidefx fixed their indexed attribute to not include empty value.
Thus we need to build a mapping between the index in the indexed attribute and
the primitive index.

appleseedhq/cortex,appleseedhq/cortex,appleseedhq/cortex