Missing term in list

In Ideal mode, a directive that can accept multiple arguments (EXTRN,
PUBLIC, and so on) separated by commas does not have an argument after one
of the commas in the list. For example,

   EXTRN XXX:BYTE,,YYY:WORD 

In Ideal mode, all argument lists must have their elements separated by
precisely one comma, with no comma at the end of the list.