Is the reality of zero morphs controversial among linguists? I haven't been able to find a wealth of information online about zero morphs, but did find a definition of them at the SIL Glossary of Linguistic Terms, which read as follows:
"zero morph is a morph, consisting of no phonetic form, that is proposed in some analyses as an allomorph of a morpheme that is ordinarily realized by a morph having some phonetic form. Example (English)"
example: "The plural form that is realized in two sheep is Ø, in contrast with the plural -s in two goats."
Is this analysis of singular "sheep" vs. plural "sheep" accepted by most linguists, or do linguists debate other possibilities, e.g. that the singular and plural forms of sheep happen to be identical, no zero morpheme needed?