nuke: Handle NULL Knob* in TxReaderFormat::setMipLabels
nuke: Handle NULL Knob* in TxReaderFormat::setMipLabels

bdeluca/oiio,lgritz/oiio,OpenImageIO/oiio,OpenImageIO/oiio,OpenImageIO/oiio,YangYangTL/oiio,bdeluca/oiio,lgritz/oiio,lgritz/oiio,bdeluca/oiio,YangYangTL/oiio,mcanthony/oiio,mcanthony/oiio,lgritz/oiio,micler/oiio,YangYangTL/oiio,OpenImageIO/oiio,micler/oiio,YangYangTL/oiio,micler/oiio,mcanthony/oiio,micler/oiio,bdeluca/oiio,mcanthony/oiio