The sentential marker can be omitted if the indefinite pronoun is in subject position with no other negative indefinite in post-verbal position. Compare Example 243 (where sentence negation is optional with a preverbal negative indefinite) with Example 247 (where sentential negation is required to make the utterance grammatical). Postverbal negative indefinites require sentential negation (cf. Examples 245, 246 and 247).
Source: Prescod 2013+: 12
Source: Prescod 2013+: 12
Source: Prescod 2013+: 12
Source: Prescod 2013+: 12
Source: Prescod 2013+: 12