"It looks to me more like an underlyingly empty position that in the
right circumstances may be filled by default with a prothetic glide. Its
most common habitat is a syllable lacking a consonantal onset, and the
usual slot-filler is either a glide homorganic with whatever follows
(e.g. [j]/[w] before front/back vowels, or a glottal onset -- [h] or
[?]). It isn't really a phonological zero, since it has a predictable
surface realisation." Piotr, GASIOROWSKI, POLAND

Oh, yes, the homorganic glide is another realization of the null phoneme

Tag. /'ta ØuØ/ > ['ta: ?o] <táo> (official) or ['ta: wo] <táwo> (provincial)
Tag. /ba 'ba ØiØ/ > [ba 'ba: ?e] <babáe> (official) or [ba 'ba: ye]
<babáye> (provincial) "female, woman"