Check for absence of delimiters when delimiters is None and fixed number of operands expected.

Ensure delimiters are absent where not expected. This is only checked in the case where operand count is known. This allows for the currently accepted case where there is a operand list with no delimiter and variable number of operands (which could be empty), followed by a delimited operand list.

PiperOrigin-RevId: 212202064